Sheet post-processing device, sheet post-processing system including the same, and image forming system including the same

ABSTRACT

A sheet post-processing device includes a conveying member configured to convey a sheet-like recording medium, a processing unit configured to perform a given operation upon the recording medium conveyed by the conveying member, a communication unit configured to communicate with a device external to the sheet post-processing device for the given operation performed by the processing unit, a control unit configured to control, via the communication unit, information passing between the sheet post-processing device and the external device at a desired timing, and a storing unit configured to store information of the recording medium transmitted from the external device. The control unit transmits the information at one of a timing before a discharge of the recording medium and a timing after a discharge of the recording medium.

PRIORITY STATEMENT

The present patent application claims priority under 35 U.S.C. §119 uponJapanese patent application no. 2005-238045, filed in the Japan PatentOffice on Aug. 18, 2005, no. 2005-267401, filed in the Japan PatentOffice on Sep. 14, 2005, no. 2006-001511, filed in the Japan PatentOffice on Jan. 6, 2006, and no. 2006-133744, filed in the Japan PatentOffice on May 12, 2006, the contents and disclosures of which are herebyincorporated by reference herein in their entirety.

BACKGROUND

1. Field of Invention

The present application generally relates to a sheet post-processingdevice, a sheet post-processing system including a plurality of thesheet post-processing devices, and an image forming system including thesheet post-processing system having the plurality of the above-describedsheet post-processing device.

2. Discussion of the Related Art

One image forming system employs a known technique for controlling animage forming device connected with a plurality of sheet processingdevices for stably performing a sheet processing operation.

Specifically, the image forming system includes a relay control unit ismounted between the image forming device and each sheet processingdevice so that the relay control unit can control operations of eachsheet processing device. Such a relay control unit can determine theoperation time for a corresponding sheet processing device that performsa specific function of various sheet processing operations, and, after agiven period of the operation time has elapsed, transmit information ofthe sheet processing operation to each sheet processing device.

Further, another image forming system employs a known data communicationmethod using a technique in which data transmission is controlled.

Specifically, when one peripheral device is connected with a single hostsystem or with a plurality of host systems, the data communicationmethod can cause the peripheral device to avoid the communicationtimeout with the host system. To avoid interruption of the communicationwith each host system when one peripheral device is connected to aplurality of host systems, a busy signal is output from the peripheraldevice to the host system while the peripheral device is in a conditionit cannot receive data, and the host system that has received the busysignal temporarily stops data transmission after a given timeout periodhas elapsed.

With the above-described data communication method, the peripheraldevice is caused to specify a timeout prevention period that runsshorter than the timeout period, count the timeout prevention periodstarting from the initial state of the busy signal, and reset the outputof the busy signal after the timeout prevention period has elapsed.

Further, one sheet post-processing system employs a known techniqueusing a skewing part and connecting units that perform a multistageconnection to simplify connecting mechanism and control software.

Specifically, the skewing part receives a paper sheet discharged from animage forming device in a skewed state and discharges the paper sheet toa first sheet post-processing device on the basis of one end portionthereof.

The connecting units are respectively provided in and controlled by aplurality of sheet post-processing devices so as to discharge the papersheet from the skewing part or from an upstream device connected theretoto a downstream device also connected thereto.

To transmit information of a paper sheet, for example, a paper size, arequest of sheet post-processing and so forth, to the correspondingdownstream device in a system in which a plurality of sheetpost-processing devices are connected, it is commonly known to mount arelay control unit so that the relay control unit determines respectiveappropriate operation times for the plurality of sheet post-processingdevices, and transmits the information to the corresponding sheetpost-processing device after a given period has elapsed. Thus, it ispreferable that each sheet post-processing peripheral device receivesinformation of the paper sheet before or after the paper sheet isreceived. Otherwise, it may be difficult to perform sheetpost-processing operations in high-speed and stable manner.

However, the relay control unit may require space and costs, which canbe a problem. Also, the operation times determined by the relay controlunit generally have variations due to slippage in conveying papersheets. When the degree of the variation is large, the informationcannot be transmitted at a correct timing, which can cause errors.

Further, in a sheet post-post processing system in which a plurality ofsheet post-processing devices are connected to each other, a sheetpost-processing device disposed on a further downstream side may need alonger time to receive a paper sheet from an image forming deviceconnected to a most upper sheet post-processing device.

If a driver of corresponding conveying rollers initiates the conveyingrollers at the start of conveyance of the paper sheet, a period ofrotation of the conveying rollers may become unnecessarily long.Especially when the sheet post-processing device is used for processinghigh-volume paper sheets in high speed, such unnecessary long period ofrotation of the conveying rollers may cause a shorter life of therollers.

Further, the above-described sheet post-processing system including aplurality of sheet post-processing devices is generally connected to animage forming device, forming an image forming system. Such system,however, has the same problems as described above.

SUMMARY

One of more embodiments of the present invention has been made, takingthe above-mentioned circumstances into consideration.

At least one embodiment of the present invention provides a sheetpost-processing device that includes a conveying member configured toconvey a sheet-like recording medium, a processing unit configured toperform a given operation to the recording medium conveyed by theconveying member, a communication unit configured upon communicate witha device external to the sheet post-processing device for the givenoperation performed by the processing unit, and a control unitconfigured to control, via the communication unit, information passingbetween the sheet post-processing device and the external device at adesired timing.

At least one embodiment of the present invention provides a sheetpost-processing system that includes a plurality of the above-describedsheet post-processing devices.

At least one embodiment of the present invention provides an imageforming system that includes an image forming device configured to forman image on a surface of a recording medium, and a plurality of theabove-described sheet post-processing devices.

Additional features and advantages of the present invention will be morefully apparent from the following detailed description of exampleembodiments, the accompanying drawings and the associated claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are intended to depict example embodiments ofthe present invention and should not be interpreted to limit the scopethereof. The accompanying drawings are not to be considered as drawn toscale unless explicitly noted.

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic structure of an image forming system as at leastone example embodiment of the present invention;

FIG. 2 is a schematic structure of another image forming system as atleast one example embodiment of the present invention;

FIG. 3 is a schematic structure of a sheet post-processing device,included in the image forming systems of FIGS. 1 and 2, according to atleast one example embodiment of the present invention;

FIG. 4 is a schematic structure of a sheet post-processing systemincluding a plurality of sheet post-processing devices according to atleast one example embodiment of the present invention;

FIG. 5 is a block diagram (according to at least one example embodimentof the present invention) of the sheet post-processing system of FIG. 4;

FIG. 6 is a schematic diagram showing communication timings of papersheet information during a paper sheet feeding operation according to anexample embodiment of the present invention;

FIG. 7 is a schematic diagram (according to at least one exampleembodiment of the present invention) showing communication timings ofpaper sheet information after FIG. 6;

FIG. 8 is a flowchart showing a paper sheet information receivingoperation as another example embodiment of the present invention;

FIG. 9 is a flowchart showing a paper sheet information sendingoperation as another example embodiment of the present invention;

FIG. 10 is a schematic diagram showing a start timing of drivingconveying rollers according to at least one example embodiment of thepresent invention;

FIG. 11 is a flowchart showing an operation (according to at least oneexample embodiment of the present invention) of rotating conveyingrollers of FIG. 10;

FIG. 12 is a flowchart showing a received signal storing operationaccording to an example embodiment of the present invention;

FIG. 13 is a flowchart showing a different received signal storingoperation according to another example embodiment of the presentinvention;

FIG. 14 is a flowchart showing a different received signal storingoperation according to another example embodiment of the presentinvention;

FIG. 15 is a flowchart showing an operation of transmitting a leadingedge discharging signal according to an example embodiment of thepresent invention;

FIG. 16 is a flowchart showing an operation of a task of processing afirst paper sheet of a stack of paper sheets, according to an exampleembodiment of the present invention;

FIGS. 17A and 17B are flowcharts showing respective tasks of processingsecond and third paper sheets of the stack of paper sheets of FIG. 16,according to an example embodiment of the present invention;

FIG. 18 is a flowchart showing a task of processing the leading edge ofa paper sheet, according to an example embodiment of the presentinvention;

FIG. 19 is a flowchart showing a task of processing the trailing edge ofa paper sheet, according to another example example embodiment of thepresent invention;

FIG. 20 is a schematic diagram (according to at least one exampleembodiment of the present invention) showing transmission timings ofsignals transmitted in the flowcharts of FIGS. 18 and 19;

FIG. 21 is a flowchart showing a task of processing a leading edge of afirst paper sheet, according to an example embodiment of the presentinvention;

FIG. 22 is a flowchart showing a task of processing a trailing edge of afirst paper sheet, according to another example embodiment of thepresent invention;

FIGS. 23A and 23B are flowcharts showing tasks of processing leading andtrailing edges of a second paper sheet, according to other exampleembodiments of the present invention;

FIG. 24 is a schematic diagram showing transmission timings (accordingto at least one example embodiment of the present invention) of signalstransmitted according to the flowcharts of FIGS. 21, 22, 23A and 23B;and

FIG. 25 is a flowchart of an operation of transmitting signals accordingto at least one example embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

It will be understood that if an element or layer is referred to asbeing “on”, “against”, “connected to” or “coupled to” another element orlayer, then it can be directly on, against, connected or coupled to theother element or layer, or intervening elements or layers may bepresent. In contrast, if an element is referred to as being “directlyon”, “directly connected to” or “directly coupled to” another element orlayer, then there are no intervening elements or layers present. Likenumbers referred to like elements throughout. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements describes as “below” or “beneath” otherelements or features would hen be oriented “above” the other elements orfeatures. Thus, term such as “below” can encompass both an orientationof above and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsherein interpreted accordingly.

Although the terms first, second, etc. may be used herein to describedvarious elements, components, regions, layers and/or sections, it shouldbe understood that these elements, components, regions, layer and/orsections should not be limited by these terms. These terms are used onlyto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentinvention. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“includes” and/or “including”, when used in this specification, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

In describing example embodiments illustrated in the drawings, specificterminology is employed for the sake of clarity. However, the disclosureof this patent specification is not intended to be limited to thespecific terminology so selected and it is to be understood that eachspecific element includes all technical equivalents that operate in asimilar manner.

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views, exampleembodiments of the present invention are described.

It is important to note that, in the example embodiments hereinafterdescribed, a sheet post-processing device corresponds to sheetpost-processing devices 6 a, 6 b, 6 c, 6 d, and 6 e. A conveying membercorresponds to a pair of outlet rollers 11, a pair of dischargingrollers 19, sheet stack conveying rollers 17 a and 17 b, and respectivepairs of conveying rollers 34, 35, and 36. A processing unit correspondsto a punching unit 7, a jogger fence 16, a rear end fence 31, a foldingplate 23, and a pair of folding rollers 24. A communication unitcorresponds to communication modules 6 a 2 a, 6 a 2 b, 6 b 2 a, 6 b 2 b,6 c 2 a, 6 c 2 b, 6 c 2 c, 6 d 2 a, and 6 e 2 a. A control unitcorresponds to control modules or units 6 a 1, 6 b 1, 6 c 1, 6 d 1, and6 e 1. A storing unit corresponds to storing units 6 a 3, 6 b 3, 6 c 3,6 d 3, and 6 e 3. An image forming device corresponds to an imageforming device 1.

First Example Embodiment

Referring to FIGS. 1 and 2, respective schematic structures of imageforming systems 100 and 200 that include a sheet post-processing device6 according to an example embodiment of the present invention aredescribed.

The image forming system 100 of FIG. 1 is shown in the form of a copier.The image forming system 100 includes an image forming device 1, a sheetfeeding device 2 that feeds paper sheets to the image forming device 1,and a scanner 3, and a circulation type automatic document feeder 4,both of which read an image formed on an original document. A papersheet on which an image is formed or printed by the image forming device1 is fed to an inlet guide plate in a sheet post-processing device 6 viaa relay unit 5.

A “paper sheet” is an example of a recording medium. The recordingmedium includes a recording paper, transfer sheet, OHP sheet, and soforth. In the example embodiments of the present invention, a “papersheet” represents these kinds of recording medium.

FIG. 2 is a schematic view of the image forming system 200 in the formof a printer, which is mounted neither with such the scanner 3 nor withsuch the circulation type automatic document feeder 4. Aside from thescanner 3 and the circulation type automatic document feeder 4, theimage forming system 200 has the same structural arrangement of theimage forming system 100 as the above-described copier.

The sheet post-processing device 6 is mounted on a side of the imageforming device 1, as described above. A paper sheet discharged from theimage forming device 1 is guided into the sheet post-processing device 6and then various kinds of post-processing operations are applied to thepaper sheet in accordance with the function of the sheet post-processingdevice 6. In this case, the image forming device 1 can be selected fromdevices or apparatuses having the known image forming function, forexample, an image forming device based on the electrophotographicprocess, a device including an inkjet type printing bead, or the like,and therefore detailed description thereof is omitted.

Referring to FIG. 3, a schematic structure of the sheet post-processingdevice 6 according to the present example embodiment is described.

A sheet post-processing device that can achieve the example embodimentsof the present invention is not limited to the sheet post-processingdevice 6 having the structure shown in FIG. 3. The present invention canapply a sheet post-processing device that performs an operation ofpunching, center folding, Z-folding, binding, or other sheetpost-processing operations.

As indicated by an arrow shown in FIG. 3, in the sheet post-processingdevice 6, a paper sheet received from the image forming device 1 isconveyed or forwarded through an inlet sheet conveying path A in which asheet post-processing mechanism for applying the post-processingoperations to a single paper sheet is disposed. For example, a punchingunit 7, which serves as a processing unit, in the sheet post-processingdevice 6 in FIG. 3 serves as a perforation mechanism including a hopper8.

The paper sheet is then sorted and transferred into one of an uppersheet conveying path B, an intermediate sheet conveying path C, and alower sheet conveying path D by path selectors 28 and 29 and turningguides 37 and 38.

When the paper sheet has passed the path selector 28 and the turningguide 37 into the upper sheet conveying path B, the paper sheet isconveyed through a position mounted with an upper sheet dischargingsensor 40, through a pair of outlet rollers 11, and is guided to a prooftray 22.

When the paper sheet has passed the path selector 28 and the turningguide 37 and has been guided by the path selector 29 and the turningguide 38 to the intermediate sheet conveying path C, the paper sheet isconveyed to a shift roller 13.

When the paper sheet has passed the path selector 28 and the turningguide 37 and has been guided by the path selector 29 and the turningguide 38 to the lower sheet conveying path D, the paper sheet isconveyed to a staple tray 14 where adjustment and staple bindingoperation are carried out.

Paper sheets transferred onto the staple tray 14 by respective pairs ofconveying rollers 34, 35, and 36, each of which serving as a conveyingmember, are aligned in a direction perpendicular to the paper feeddirection by a jogger fence 16 as a processing unit, and further thefeed direction of the paper sheets is adjusted with reference to a rearend fence 31, which serves as a processing unit, by a knock roller 12.

Thereafter, a sheet stack conveying roller 17 b, which serves as aconveying member and is supported by a sheet stack guide plate (notshown), approaches another sheet stack conveying roller 17 a, whichserves as a conveying member, by the rotation of the sheet stack guideplate, and thereby the sheet stack is clamped therebetween to maintainits attitude and the rear end fence 31 is shifted to the positionindicated by the broken line in FIG. 3. In the case of the end bindingprocess, the staple process is carried out at a given position, and thenfed upward by a discharge hook 15, so that the paper sheets aredischarged into an outlet tray 21 by a pair of discharge rollers 19serving as a conveying roller, and then accumulated therein.

A sheet discharge sensor 46 detects the condition of discharging thepaper sheets to the outlet tray 21, and a sheet surface detection sensor47 detects the amount of accumulated paper sheets on the outlet tray 21.

In the first example embodiment, when the top sheet of the accumulatedpaper sheets has reached to a given height, the outlet tray 21 is movedto a downward direction by a fixed or given amount so that a furtheramount of paper sheets can be accumulated.

Further, a hook position detection sensor 45 detects the home positionof the discharge hook 15. Based on the result of the above-describeddetection, a discharge belt 18 is controlled.

In the case of the saddle stitching process, the sheet stack is adjustedregarding the position, and fed downward, after the paper sheets arepinched by the pair of sheet stack conveying rollers 17 a and 17 b. Atthe end of the saddle stitching process, the paper sheets are fed to afolding position by sheet stack conveying rollers 30 a and 30 b, and themiddle folding process is carried out, using a folding plate 23 and apair of folding rollers 24, both serve as a processing unit. Thereafter,the paper sheets are fed to a center-folded sheet discharging tray 27 bya center-folded sheet discharging roller 26, and then stacked therein.

In the inlet sheet conveying path A, which is commonly disposed upstreamwith respect to the upper sheet conveying path B, the intermediate sheetconveying path C, and the lower sheet conveying path D, an inlet sensor39 for detecting a paper sheet supplied from the image forming device 1is disposed, and a pair of conveyor rollers 32 and the punching unit 7are disposed downstream thereto, and further the path selector 28 andthe turning guide 37 are disposed downstream thereto.

The path selector 28 is maintained in the state shown by a solid line inFIG. 3 by a spring (not shown). When a solenoid (not shown) is turnedon, the path selector 28 rotates counterclockwise, as indicated by analternate long and short dashed lines shown in FIG. 3, so that papersheets are sorted into the lower sheet conveying path D. When thesolenoid is turned off, the paper sheets are sorted into the upper sheetfeeding path B.

The path selector 29 is maintained in the state shown by a solid line inFIG. 3 by another spring (not shown). When another solenoid (not shown)is turned on, the path selector 29 rotates clockwise, as indicated by analternate long and short dashed lines shown in FIG. 3, so that the papersheets are sorted into the intermediate sheet conveying path C. When thesolenoid is turned off, the paper sheets are further fed to the lowersheet conveying path D, and fed by the pairs of conveying rollers 34 and35.

The turning guides 37 and 38 have a roller shape so as to guide thepaper sheets to smoothly turn at a sharp angle and serve to assist thesorting of the paper sheets by the path selectors 28 and 29. In thiscase, paper sheets in a direction changed by the path selectors 28 and29 come into contact with the turning guides 37 and 38, and then aremoved together therewith. Accordingly, the turning guides 37 and 38serve to reduce the feeding resistance for the paper sheet at abranching section having a smaller radius of nature.

In the intermediate sheet conveying path C, the shift roller 13 ismounted, which roller is capable of moving the paper sheets by aspecified distance in a direction perpendicular to the feedingdirection. In the shift roller 13, the shift function results from themovement of the paper sheets in the direction perpendicular to thefeeding direction by a driving unit (not shown).

The movement of the paper sheets transferred to the intermediate sheetconveying path C by a pair of conveying rollers 33 and the turningroller 38 by the shift roller 13 by such a specified distance in thedirection perpendicular to the feeding direction causes to provide anappropriate amount of shift for the paper sheets both in the feedingdirection and in the direction perpendicular thereto, so that the papersheets are discharged by the pair of discharge rollers 19 serving as aconveying member, preset the shifted state, one end portion of which issupported rotatably with respect to the sheet discharge guide plate 20,and then stacked in the outlet tray 21. In this case, the timing in theabove processes is determined on the basis of the paper detectioninformation from a roller shift sensor 41, the sheet size informationand others.

In the lower sheet conveying path D, a staple tray sheet dischargesensor 43 is mounted. The paper discharging sensor 43 makes it possibleto detect whether or not a sheet of paper exists in the lower sheetconveying path D. In this case, a paper detecting signal may be used asa trigger signal for aligning the paper sheet when discharging the papersheet into the staple tray 14.

The paper sheets transferred to the lower sheet conveying path D aresequentially fed by the pairs of conveyor rollers 34, 35 and 36, andaligned in the staple tray 14 after stacked.

The trailing end of the paper sheets discharged into the staple tray 14is adjusted with reference to the rear end fence 31.

The rear end fence 31 is designed so as to rotate around the center axisof the sheet stack conveying roller 17 a. In the case of stacking thepaper sheets into a sheet stack, one end portion of the rear end fence31 on the solenoid side is moved by a solenoid, and the other endportion of the rear end fence 31 is inserted into the feed line, therebyenabling the paper sheets to be stacked into a sheet stack.

The paper sheets stacked in the staple tray 14 are temporarily droppedor moved downward by the knock roller 12, and then the lower end thereofis aligned.

The knock roller 12 receives an oscillating motion with respect to thecenter at a supporting point 12 a from a knock solenoid (not shown).Such an oscillating motion intermittently acts on the paper sheetssupplied to the staple tray 14 to collide them with the rear end fence31. In this case, the knock roller 12 rotates such that the paper sheetrotated counterclockwise by a timing belt moves towards the rear endfence 31.

The alignment of the paper sheets stacked in the staple tray 14 in thedirection perpendicular to the feed direction is carried out by joggerfences 16.

The jogger fences 16 are driven via the timing belt by a rotationreversible jogger motor (not shown), and reciprocally move in thedirection perpendicular to the paper feed direction. The pressing of theend surface of the sheet stack by the mov ement causes the paper sheetsto be aligned in the direction perpendicular to the feed direction. Thisaction is carried out either during the stacking process or after finalsheets has been stacked in accordance with requirement.

A sheet detection sensor 44 mounted on the staple tray 14 is used as aso-called sheet detecting sensor for detecting whether or not a sheet ofpaper exists on the staple tray 14. The knock roller 12, the rear endfence 31, and the jogger fences 16 constitutes an alignment mechanismfor aligning the sheet stack both in a direction parallel to the paperfeed direction and in a direction perpendicular thereto.

The pairs of sheet stack conveying rollers 17 a, 17 b, 30 a, and 30 bcause a mechanism (not shown) to apply a press and release action. Afterthe sheet stack passes between the pairs of conveying rollers 17 a, 17b, 30 a, and 30 b in the release state, these rollers 17 a, 17 b, 30 a,and 30 b press the sheet stack and then convey them. The pairs of sheetstack conveying rollers 17 a, 17 b, 30 a, and 30 b are capable ofbecoming either in or out of contact with each other by a pressurerelease motor (not shown).

Furthermore, the pairs of sheet conveying rollers 17 a, 17 b, 30 a, and30 b are rotated by a stepping motor (not shown), a pulley (not shown),and a timing belt (not shown). The feeding distance of the sheet stackcan be adjusted by controlling the rotation rate of the stepping motor.Both of the pair of sheet stack conveying rollers 17 a and 17 b and thepair of sheet stacking conveying rollers 30 a and 30 b can be separatelydisposed in a pair wise manner, and the press contact distancetherebetween can be freely adjusted.

As shown in FIG. 3, the staple unit 9 includes a stitcher 9 a (in thisspecification, the unit is referred to as a stitcher, although it istraditionally referred as a driver) for projecting a needle and aclincher 9 b for bending the end portion of the needle driven into thesheet stack. In the present embodiment, the stitcher 9 a and theclincher 9 b are separately structured and the staple unit 9 issupported movably in the direction perpendicular to the sheet stack feeddirection by a stapler moving guide 10. Moreover, the stitcher 9 a andthe clincher 9 b include a mutual position determining mechanism and amovement driving mechanism (both not shown).

The staple position of the sheet stack in the feed direction isdetermined from the conveying of the sheet stack by the pair of sheetstack conveying rollers 17 a and 17 b. Thereby, the staple can bestopped at various positions for the sheet stack.

In FIG. 3, a middle folding mechanism is positioned downstream in thesheet conveying direction for the staple unit 9 (downstream in the caseof folding the paper sheet, and spatially the under side). The middlefolding mechanism includes the pair of folding rollers 24, the foldingplate 23, and a stopper 25. In the upstream portion of the staple unit9, a sheet stack stapled at the center of the paper sheet in the feeddirection is conveyed by the pair of sheet stack conveying rollers 17 aand 17 b until it comes into contact with the stopper 25, and then thereference position for folding the sheet stack is determined bytemporarily releasing the nipping pressure of the sheet stack conveyingroller 17 b. Thereafter, the sheet stack is held by applying the nippingpressure between the pair of sheet stack conveying rollers 30 a and 30 bthereto, and then the stopper 25 is moved back and decoupled from thetrailing end of the sheet stack, so that the sheet stack is conveyed bya given distance and set in the folding position on the basis of thesheet size signal supplied from the main body of the image formingdevice 1. The sheet stack, which is conveyed to the folding position(normally the center of the sheet stack in the sheet feeding direction)and stopped there, is inserted into a spacing between the pair offolding rollers 24 by the folding plate 23, so that the pair of foldingrollers 24 causes the sheet stack to be folded at the center by pressingand rotating the sheet stack. In this case, if the sheet stack by alarger size, it is conveyed to a downstream position in the feeddirection by a greater distance than at the position of the stopper 25.

In this embodiment, the sheet conveying path on the downstream sidecurved at an area far away from the stopper 25 to guide the end of thesheet stack into the horizontal direction. Such a structural arrangementallows the sheet stack to be conveyed, even if it has a larger size,thereby making it possible to decrease the size of the paper sheetpost-processing device 6 in the height direction.

As shown in FIG. 3, the stopper 25, which serves as an alignmentmechanism is designed such that the stopper 25 can be rotated around thecenter axis of the sheet stack conveying roller 30 a, and that the endportion of the stopper 25 on the solenoid side is driven by thesolenoid, and the end portion is away from the sheet conveying path.

The folded sheet stack is discharged into a center-folded sheetdischarging tray 27 by a center-folded sheet discharging roller 26, andthen stacked therein.

Sensors 48 and 49 in the center-folded section detect whether or not asheet of paper exists therein.

Moreover, a sensor 51 in the center-folded sheet discharging tray 27detects whether or not the sheet stack is placed on the center-foldedsheet discharging tray 27. It is used to count the number of sheetstacks discharged from the empty state and to monitor the full state ofthe center-folded sheet discharging tray 27.

A fold end stopper position detecting sensor 50 detects the end positionof the sheet stacks in the case when the stopper 25 is either activatedor deactivated.

FIG. 4 shows a schematic structure of a sheet post-processing system 300in which a plurality of sheet post-processing devices 6 a, 6 b, 6 c, 6d, and 6 e are connected, along with the accompanying image formingdevice 1.

In the present example embodiment, the image forming device 1 isconnected with a document feeding device 4, a high-volume sheet feedingdevice 2, and a plurality of sheet post-processing devices or firstthrough fifth sheet post-processing devices 6 a, 6 b, 6 c, 6 d, and 6 e.The first sheet post-processing device 6 a is connected with oneupstream device, which is the image forming device 1, and one downstreamdevice, which is the second sheet post-processing device 6 b. The secondsheet post-processing device 6 b is also connected with one upstreamdevice, which is the first sheet post-processing device 6 a, and onedownstream device, which is the third sheet post-processing device 6 c.The third sheet post-processing device 6 c is connected with oneupstream device, which is the second sheet post-processing device 6 b,and two downstream devices, which are the fourth and fifth sheetpost-processing devices 6 d and 6 e. The fourth sheet post-processingdevice 6 d is the most downstream device and is connected with oneupstream device, which is the third sheet post-processing device 6 c.The fifth sheet post-processing device 6 d is the most downstream deviceand is connected with one upstream device, which is the third sheetpost-processing device 6 c.

FIG. 5 shows a block diagram of the sheet post-processing system 300 inwhich various modules or units including respective communicationmodules for the first through fifth sheet post-processing devices 6 athrough 6 e are described.

Each of the first through fifth sheet post-processing devices 6 athrough 6 e includes one communication module or unit with respect toone device connected with itself. Specifically, the first sheetpost-processing device 6 a includes first and second communicationmodules 6 a 2 a and 6 a 2 b. The second sheet post-processing device 6 bincludes first and second communication modules 6 b 2 a and 6 b 2 b. Thethird sheet post-processing device 6 c includes first, second, and thirdcommunication modules 6 c 2 a, 6 c 2 b, and 6 c 2 c. The fourth sheetpost-processing device 6 d includes a first communication modules 6 d 2a. The fifth sheet post-processing device 6 e includes a firstcommunication module 6 e 2 a.

The sheet post-processing devices 6 a, 6 b, 6 c, 6 d, and 6 e alsoinclude control modules or units 6 a 1, 6 b 1, 6 c 1, 6 d 1, and 6 e 1,respectively, serving as a transmission unit for sending and receivingdata at respectively given timings or intervals.

Further, the sheet post-processing devices 6 a, 6 b, 6 c, 6 d, and 6 einclude storing units 6 a 3, 6 b 3, 6 c 3, 6 d 3, and 6 e 3,respectively, for arbitrarily storing and reading respective receivedsignals.

As a transmission method, it is general to employ a serial communicationusing, for example, a UART (Universal Asynchronous ReceiverTransmitter).

A memory or a hard disk drive (HDD) is used as a storing unit accordingto the volume of data to be stored therein. In the example embodiment ofthe present invention, a memory and a HDD are used. However, any otherstoring unit that can temporarily store target information may beapplied to the present invention.

Each of the control modules 6 a 1, 6 b 1, 6 c 1, 6 d 1, and 6 e 1includes a central processing unit (CPU) (not shown), a read-only memory(ROM) (not shown), and a random access memory (RAM) (not shown). In thecontrol performed in the respective control modules or units 6 a 1, 6 b1, 6 c 1, 6 d 1, and 6 e 1, the CPU executes programs stored in the ROMby using the RAM as a working area, and thus the control of each of thesheet post-processing devices 6 a, 6 b, 6 c, 6 d, and 6 e is carriedout, based on the programs.

Referring to FIGS. 6 and 7, schematic diagrams showing communicationtimings of paper sheet information during a paper sheet feedingoperation are described according to the first example embodiment of thepresent invention.

In FIGS. 6 and 7, the reference number “P1”, “P2”, “P3”, “P4”, “P5”, and“P6” represent respective paper sheets that are conveyed in the sheetpost-processing devices 6 a, 6 b, and 6 c.

When a paper sheet, for example a paper sheet P1, is fed from the imageforming device 1 shown in FIGS. 1, 2, and 4 to the first sheetpost-processing device 6 a, the communication module 6 a 2 a of thefirst sheet post-processing device 6 a receives paper sheet informationfrom the image forming device 1 and stores the paper sheet informationin the first storing unit 6 a 3 thereof. The paper sheet informationcontains information for use in processing the paper sheet fed from theimage forming device 1, for example, the size, thickness, ID, a requestof sheet post-processing operation to a specific sheet post-processingdevice, and so forth.

The first sheet post-processing device 6 a receives a paper sheet,performs the sheet post-processing operation according to a request ofsheet post-processing operation issued from the image forming device 1,and conveys or forwards the processed paper sheet to the second sheetpost-processing device 6 b, which is a downstream device of the firstsheet post-processing device 6 a. When no request of sheetpost-processing operation to be performed in the first sheetpost-processing device 6 a has been issued, the first sheetpost-processing device 6 a performs no specific sheet post-processingoperation and simply forwards the paper sheet to the second sheetpost-processing device 6 b.

When a paper sheet is to be discharged to the outside of the first sheetpost-processing device 6 a, for example, when the leading edge of apaper sheet comes at a specified position, such as the pair of outletrollers 11 serving as a conveying member in the present exampleembodiment, the first sheet post-processing device 6 a transmits thepaper sheet information stored in the first storing unit 6 a 3, to thesecond sheet post-processing device 6 b. Through the above-descriedtransmission, the second sheet post-processing device 6 b can obtain thepaper sheet information before receiving the paper sheet. Thereby, thesecond sheet post-processing device 6 b can perform its sheetpost-processing operation under the proper and stable condition.Further, even when the content of a request of the sheet post-processingoperation is changed, the sheet post-processing operation can avoidunnecessary interruption. Thereby, a series of sheet post-processingoperations can be performed in high and stable speed.

When the paper sheet processed in or passed through the first sheetpost-processing device 6 a is fed, the second sheet post-processingdevice 6 b receives the paper sheet information from the first sheetpost-processing device 6 a and stores the paper sheet information in thesecond storing unit 6 b 3 thereof. When discharging or forwarding thepaper sheet to the third sheet post-processing device 6 c, the secondsheet post-processing device 6 b transmits the paper sheet informationstored in the second storing unit 6 b 3, to the third sheetpost-processing device 6 c.

As shown in FIG. 7, the sheet post-processing device 6 c performs theoperation similar to those performed by the first and second sheetpost-processing devices 6 a and 6 b. That is, when the paper sheetprocessed in or passed through the second sheet post-processing device 6b is fed, the third sheet post-processing device 6 c receives the papersheet information from the second sheet post-processing device 6 b andstores the information in the third storing unit 6 c 3 thereof. And,when the paper sheet is discharged to the outside of the third sheetpost-processing device 6 c or to one of the sheet post-processingdevices 6 d and 6 e connected thereto as shown in FIGS. 4 and 5, thethird sheet post-processing device 6 c transmits the paper sheetinformation stored in the third storing unit 6 c 3, to the downstreamsheet post-processing device.

The method of transmitting the paper sheet information is not limited tothe above-described method but other various ways may be applied to thepresent invention. In FIGS. 6 and 7 of the present example embodiment ofthe present invention, for example, a paper sheet forwarding signal istransmitted to the downstream device after the paper sheet informationhas been sent. The downstream device can confirm the paper sheetinformation by receiving the paper sheet forwarding signal.

Referring to a flowchart of FIG. 8, a procedure of a paper sheetinformation receiving operation is described. The paper sheetinformation receiving operation is performed such that a currentlyoperating device or a local sheet post-processing device, which isconnected to an upstream device and a downstream device, receives papersheet information during the paper sheet feeding operation.

In the example embodiments of the present invention, the “local sheetpost-processing device” represents any one of the first, second, andthird sheet post-processing devices 6 a, 6 b, and 6 c while the fourthand fifth sheet post-processing devices 6 d and 6 e are the mostdownstream devices, as shown in FIGS. 4 and 5.

As previously described, the sheet post-processing operations arecontrolled by the CPU (not shown) of the control module or unit of eachsheet post-processing device. In the present example embodiment, the CPUof the local first sheet post-processing device basically controls theoperations of the following flowcharts.

At the start of the paper sheet information receiving operation of FIG.8, the CPU of the local sheet post-processing device determines whetherthe local sheet post-processing device has received the paper sheetinformation from an upstream device of the local sheet post-processingdevice in step S101.

When the local sheet post-processing device has received the paper sheetinformation from the upstream device, the determination result in stepS101 is YES, and the process goes to step S102.

When the local sheet post-processing device has not yet received thepaper sheet information from the upstream device, the determinationresult in step S101 is NO, and the process of step S101 repeats untilthe local sheet post-processing device receives the paper sheetinformation.

The CPU temporarily writes the paper sheet information, including thesize, thickness, ID, the request of sheet post-processing operation, andso forth, in a storing unit of the local sheet post-processing device instep S102, and determines whether the local sheet post-processing devicehas received the paper sheet forwarding signal in step S103.

When the local sheet post-processing device has received the paper sheetforwarding signal from the upstream device, the determination result instep S103 is YES, and the process goes to step S104.

When the local sheet post-processing device has not yet received thepaper sheet forwarding signal from the upstream device, thedetermination result in step S103 is NO, and the process of step S103goes back to step S101.

In step S104, the CPU confirms the paper sheet information and storesthe information in the storing unit.

Referring to a flowchart of FIG. 9, a procedure of a paper sheetinformation sending operation is described. The paper sheet informationsending operation is performed by the local sheet post-processing deviceto transmit paper sheet information during the paper sheet feedingoperation.

At the start of the paper sheet information sending operation of FIG. 9,the CPU of the local sheet post-processing device determines whether theleading edge of the paper sheet has come at a specified position of thepaper sheet.

When the leading edge of the paper sheet has come at the specifiedposition, the determination result in step S201 is YES and the processgoes to step S202.

When the leading edge of the paper sheet has not yet come at thespecified position, the determination result in step S201 is NO and theprocess of step S201 repeats until the leading edge of the paper sheetcomes at the specified portion.

The CPU transmits the paper sheet information that is stored in thestoring unit of the local sheet post-processing device in step S202, andtransmits the paper sheet forwarding signal to the downstream device instep S203.

As described above, each sheet post-processing device of the presentexample embodiment receives corresponding paper sheet information,stores the received information, and transmits the stored informationwhen discharging the paper sheet to the downstream device. However,information other than the information necessary for each paper sheet,for example, information of destination, a speed of conveying the papersheet, and so forth, is not necessarily transmitted during the sheetfeeding operation. That is, in this case, the local sheetpost-processing device can transmit information other than theinformation necessary for each paper sheet, to the downstream deviceinstantly on receiving the information.

Referring to FIG. 10, a schematic diagram is described to show a starttiming of driving the pair of conveying rollers 32, which have beenstopped, of the second sheet post-processing device 6 b. The specificdiagram of FIG. 10 shows one example of the roller driving operation,which also can be applied to the operation performed between the first,second, third, fourth, and fifth sheet post-processing devices 6 a, 6 b,6 c, 6 d, and 6 e.

When the image forming device 1 starts the paper sheet feeding operationwith respect to the first sheet post-processing device 6 a, the pair ofsheet conveying rollers 32 of the second sheet post-processing device 6b still remains stopped.

When the first sheet post-processing device 6 a discharges a paper sheetto the second sheet post-processing device 6 b, the paper sheetinformation followed by the paper sheet forwarding signal istransmitted.

The second sheet post-processing device 6 b starts rotating the pair ofconveying rollers 32 when receiving the paper sheet information followedby the paper sheet forwarding signal.

With the above-described operation, the pair of conveying rollers 32 canprevent the rotations thereof for an unnecessarily long time, which canextend the lives of the rollers and other parts. That is, by startingthe rotation of the pair of conveying rollers 32 at the receipt of thepaper sheet information by the communication module 6 b 2 a of thesecond sheet post-processing device 6 b, the rotation period of the pairof conveying rollers 32 may become shorter and the lives of the pair ofconveying rollers 32 may become longer.

Referring to a flowchart of FIG. 11, a procedure of an operation ofrotating conveying rollers that have not been rotated is described.

In step S301 of the flowchart in FIG. 11, the CPU of a local sheetpost-processing device determines whether the pair of conveying rollersthereof remains stopped.

When the pair of conveying rollers is stopped, the determination resultin step S301 is YES, and the process goes to step S302.

When the pair of conveying roller is rotated, the determination resultin step S301 is NO, and the CPU completes the procedure.

In step S302, the CPU determines whether the local sheet post-processingdevice has received the paper sheet forwarding signal.

When the local sheet post-processing device has received the paper sheetforwarding signal, the determination result in step S302 is YES, and theprocess goes to step S303.

When the local sheet post-processing device has not yet received thepaper sheet forwarding signal, the determination result in step S302 isNO, and the process of step S302 repeats until the local sheetpost-processing device receives the paper sheet forwarding signal.

In step S303, the CPU initiates the rotation of the pair of conveyingrollers, and completes the procedure.

Second Example Embodiment

Referring to a flowchart of FIG. 12, a communication procedure of areceived signal storing operation is described according to a secondexample embodiment of the present invention. The received signal storingoperation is performed by the local sheet post-processing device totransmit a signal from the upstream device during the paper sheetfeeding operation.

At the start of the received signal storing operation of the flowchartof FIG. 12, the CPU of the local sheet post-processing device determineswhether the local sheet post-processing device has received variousinformation signals from the upstream device. The various informationsignals include the paper sheet information for use in processing thepaper sheet fed from the upstream device, for example, paper sheetinformation of the size, thickness, ID, a request of sheetpost-processing operation to a specific sheet post-processing device,and so forth. The various information signals can include a singleinformation signal even through the term is used in plural in theexample embodiments of the present invention.

When the local sheet post-processing device has received variousinformation signals from the upstream device, the determination resultin step S401 is YES, the process goes to step S402.

When the local sheet post-processing device has not yet received variousinformation signals from the upstream device, the determination resultin step S401 is NO, the process of step S401 repeats until the localsheet post-processing device receives the various information signals.

In step S402, the CPU temporarily writes the received informationsignals in a storing unit of the local sheet post-processing device, andthe process goes to step S403.

The local sheet post-processing device receives the paper sheet, conveysthe paper sheet therein, performs the sheet post-processing operationaccording to the request of the sheet post-processing operationcontained in the paper sheet information, and discharges or forwards thepaper sheet to the downstream device. When no request of sheetpost-processing operation corresponding to the local sheetpost-processing device is received, the local sheet post-processingdevice simply transmits the paper sheet to the downstream device withoutperforming any sheet post-processing operation therein.

In step S403, the CPU of the local sheet post-processing devicedetermines whether the processed paper sheet has come at a specifiedposition, for example, whether the leading edge of the paper sheet hasbeen present at or in the vicinity of the pair of outlet rollers 11.

When the leading edge of the paper sheet is present at or in thevicinity of the pair of outlet rollers 11, the determination result instep S403 is YES and the process goes to step S404.

When the leading edge of the paper sheet is not present at or in thevicinity of the pair of outlet rollers 11, the determination result instep S403 is NO and the process of step S403 goes back to step S401.

The CPU transmits the information signals including the paper sheetinformation stored in the storing unit, to the downstream device in stepS404, and determines whether the signal transmission has been completedin step S405.

When the signal transmission has been completed, the determinationresult in step S405 is YES and the CPU completes the process.

When the signal transmission has not yet been completed, thedetermination result in step S405 is NO, and the process goes back tostep S401.

According to the above-described operation, the downstream device canreceive the information signals including the paper sheet information ofthe corresponding paper sheet. Therefore, the downstream device canperform the sheet post-processing operation in a proper and stablemanner. Further, even when the paper sheet information of thecorresponding paper sheet has been changed, the sheet post-processingoperation can be continuously performed without temporarily stopping theoperation. Therefore, a high-speed sheet post-processing operation canbe performed.

Similar to the operation described above, when the downstream device hasreceived various information signals from the local sheetpost-processing device, the downstream device temporarily writes thepaper sheet information included in the received various informationsignals, into the storing unit of the downstream device. When the papersheet has come at a specified position, for example, when the leadingedge of the paper sheet is present at or in the vicinity of the pair ofoutlet rollers 11, the downstream device transmits the informationsignals stored therein to a further downstream device connected to thedownstream device.

As previously described, in the second example embodiment of the presentinvention, each sheet post-processing device includes the correspondingstoring unit for temporarily writing or storing a portion of or wholeinformation signals received from the upstream device with respect tothe local sheet post-processing device. When the whole sheetpost-processing devices except the most downstream device receiveinformation signals from the upstream device during the sheet feedingoperation, the sheet post-processing devices except the most downstreamdevice temporarily write the various information signals to thecorresponding storing unit, and transmits the portion of or wholeinformation signals stored therein, according to the position of thepaper sheet in the local sheet post-processing device. Therefore, thedownstream device can perform the sheet post-processing operation in anaccurate and stable manner. Further, when the content of the paper sheetinformation of the corresponding paper sheet has been changed, the sheetpost-processing operation can be continuously performed withouttemporarily stopping. Therefore, a high-speed sheet post-processingoperation can be performed.

Referring to a flowchart of FIG. 13, a different communication procedureof the received signal storing operation is described according toanother example of the second example embodiment of the presentinvention. The received signal storing operation is performed by thelocal sheet post-processing device to transmit information signals oneby one by a fixed or given amount or length of byte thereof, from theupstream device during the paper sheet feeding operation.

At the start of the received signal storing operation of the flowchartof FIG. 13, when the local sheet post-processing device receives variousinformation signals from the upstream device, the local sheetpost-processing device temporarily writes the received informationsignals in the storing unit thereof. At this time, the informationsignals are stored in an orderly sequence so as to easily recognize thereceipt order of the received information signals.

In each storing unit of the sheet post-processing devices, a series ofstorage areas are provided to write information signals received fromthe upstream device. Each storage area is basically provided for aseries of various information signals of one paper sheet. In this case,the storing unit of the local sheet post-processing device provides astorage area A having addresses including a top address “a”. Theaddresses of the storage area A are represented by a variable “A”. Thevarious information signals received by the local sheet post-processingdevice are temporarily written into the storage area A one by one in theorderly sequence starting from the top address “a”. That is, the writingof the various information signals starts from the address having thesmallest number.

When the paper sheet has come at a specified position, for example, whenthe leading edge of a paper sheet is present at or in the vicinity ofthe pair of outlet rollers 11, the local sheet post-processing devicetransmits the various information signal including the paper sheetinformation stored therein to the downstream device. Also at this time,the received information signals are sequentially read out starting fromthe top address “a” and are transmitted in the orderly sequence thereofto the downstream device.

Specifically, according to the flowchart of FIG. 13, the CPU of thelocal sheet post-processing device specifies the variable “A”representing the storage area A so as to assign the top address “a”thereto in step S501, and determines whether the local sheetpost-processing device has received a fixed or given amount of variousinformation signals transmitted from the upstream device.

When the local sheet post-processing device has received the fixedamount of various information signals, the determination result in stepS502 is YES and the process proceeds to step S503.

When the local sheet post-processing device has not yet received variousinformation signals, the determination result in step S502 is NO and theprocess of step S502 repeats until the local sheet post-processingdevice receives a fixed or given amount of information signals.

The CPU temporarily writes the received information signal in the topaddress “a” in step S503, and increments the variable “A” by one as afixed or given amount of the information signals in step S504, and theprocess proceeds to step S505.

In step S505, the CPU determines whether the paper sheet has come at thespecified position.

When the paper sheet has come at the specified position, thedetermination result in step S505 is YES and the process proceeds tostep S506.

When the paper sheet has not yet come at the specified position, thedetermination result in step S505 is NO, and the process of step S505goes back to step S502. The CPU repeats the steps S502 through S505until no more sequential information signals of the corresponding papersheet is transmitted.

After the determination result in step S505 becomes “YES”, the CPUassigns the top address “a” to the variable “A” in step S506, reads outand transmits the received information signal from the top address “a”to the downstream device in step S507. The CPU then increments thevariable “A” by one as the fixed amount of the information signals instep S508, and the process proceeds to step S509.

In step S509, the CPU determines whether the local sheet post-processingdevice has completed the transmission of the information signals withrespect to the downstream device.

When the local sheet post-processing device has completed thetransmission of the information signals, the determination result instep S509 is YES, and the CPU terminates the sheet post-processingoperation in the local sheet post-processing device.

When the local sheet post-processing device still has the informationsignals to be transmitted to the downstream device, the determinationresult in step S509 is NO, and the process goes back to step S507 torepeat steps S507 through S509 until no more sequential informationsignal to be transmitted for the corresponding paper sheet remains inthe storing area A of the storing unit of the local sheetpost-processing device.

Similar to the operation performed by the local sheet post-processingdevice, when receiving various information signals from the local sheetpost-processing device, the downstream device temporarily writes thepaper sheet information included in the received information signals,into the storing unit thereof. When the paper sheet has come at thespecified position, for example, when the leading edge of the papersheet is present at or in the vicinity of the pair of outlet rollers 11,the downstream device transmits the information signals stored thereinto the further downstream device. Also in this case, the CPU controls totransmit the information signals in the orderly sequence thereof.

When a plurality of information signals that are not properly managedare transmitted at one time, the sequence order of the signals may bechanged. The above-described condition may cause, for example, thedisorder of the requests.

In a case in which a signal A represents a signal to indicate therequest of the sheet post-processing operation and a signal B representsa signal to fix the request, when the order of the signal A and thesignal B is reversed, the fixing timing of the request may change.

Specifically, when the signal A comes before the signal B, which is thecorrect sequence order, the request of the sheet post-processingoperation indicated by the signal A may be fixed when the signal B isreceived.

On the contrary, when the signal A has not been received before thesignal B is received, which is the incorrect order, the requestindicated by the signal A may not be fixed until the next signal B isreceived.

To avoid the above-described problem causing the transmission of signalsin the incorrect order, the signals of the present example embodimentcan be controlled to properly manage the addresses stored in the storagearea, thereby the signals can be kept in the orderly sequence.

Referring to a flowchart of FIG. 14, a different communication procedureof a received signal storing operation is described according to anotherexample of the second example embodiment of the present invention. Thereceived signal storing operation is performed by the local sheetpost-processing device to transmit a signal from the downstream deviceduring the paper sheet feeding operation.

In the communication procedure of FIG. 14, the paper sheet forwardingsignal is provided for informing a timing of forwarding a paper sheet.

When the paper sheet has come at the specified position, for example,when the leading edge of a paper sheet is present at or in the vicinityof the pair of outlet rollers 11, the local sheet post-processing devicetransmits the paper sheet forwarding signal to the downstream device. Byreceiving the paper sheet forwarding signal, the downstream device canrecognize a timing of a paper sheet to be fed.

Similar to the communication procedures shown in FIGS. 12 and 13, thepaper sheet information including the size, thickness, ID, the requestof the sheet post-processing operation, and so forth are temporarilywritten or stored in the storage area A in the storing unit of the localsheet post-processing device, and transmitted while keeping the orderlysequence with respect to the paper sheet forwarding signal. Respectivetransmission timings of signals other than the paper sheet forwardingsignal are sequentially transmitted immediately before or after thepaper sheet forwarding signal. Hereinafter, signals other than the papersheet forwarding signal are referred to as “information signals” todistinguish from the paper sheet forwarding signal.

The communication procedure in the flowchart of FIG. 14 is basicallysimilar to the procedure shown in the flowchart of FIG. 13, except thatthe communication procedure of FIG. 14 uses the paper sheet forwardingsignal.

Specifically, according to the flowchart of FIG. 14, the CPU of thelocal sheet post-processing device specifies the variable “A”representing the storage area A so as to assign the top address “a”thereto in step S601, and the process proceeds to step S602.

In step S602, the CPU determines whether the local sheet post-processingdevice has received an information signal of various information signalstransmitted from the upstream device.

When the local sheet post-processing device has received a fixed orgiven amount of various information signals, the determination result instep S602 is YES and the process proceeds to step S603.

When the local sheet post-processing device has not yet received variousinformation signals, the determination result in step S602 is NO, andthe process of step S602 repeats until the local sheet post-processingdevice receives information signals.

The CPU temporarily writes the received information signal in the topaddress “a” in step S603, and increments the variable “A” by one as thefixed amount of the information signals in step S604, and the processproceeds to step S605.

In step S605, the CPU determines whether the paper sheet forwardingsignal has been received.

When the paper sheet forwarding signal has been received, thedetermination result in step S605 is YES, and the process goes to stepS606.

When the paper sheet forwarding signal has not yet been received, thedetermination result in step S605 is NO, and the process goes back tostep S602.

In step S606, the CPU determines whether the paper sheet has come at thespecified position.

When the paper sheet has come at the specified position, thedetermination result in step S606 is YES, and the process proceeds tostep S607.

When the paper sheet has not yet come at the specified position, thedetermination result in step S606 is NO, and the process of step S606repeats until the paper sheet comes at the specified position.

After the determination result in step S606 becomes “YES”, the CPUassigns the top address “a” to the variable “A” in step S607, reads outand transmits the received information signal by the fixed amount ofinformation signals, from the top address “a” to the downstream devicein step S608. The CPU then increments the variables “A” by one in stepS609, and the process proceeds to step S610.

In step S610, the CPU determines whether the local sheet post-processingdevice has completed the transmission of the information signals to thedownstream device.

When the local sheet post-processing device has completed thetransmission of the information signals, the determination result instep S610 is YES, and the process goes to step S611.

When the local sheet post-processing device still has the informationsignals to be transmitted to the downstream device, the determinationresult in step S610 is NO, and the process goes back to step S608 torepeat steps S608 through S610 until no more sequential informationsignal to be transmitted for the corresponding paper sheet remains inthe storing area A of the storing unit.

The CPU then transmits the paper sheet forwarding signal in step S611,and terminates the sheet post-processing operation in the local sheetpost-processing device.

Similar to the operation performed by the local sheet post-processingdevice, when receiving various information signals from the local sheetpost-processing device, the downstream device temporarily writes thepaper sheet information included in the received information signals,into the storing unit thereof. When the paper sheet has come at thespecified position, for example, when the leading edge of the papersheet is present at or in the vicinity of the pair of outlet rollers 11,the downstream device transmits the information signals stored thereinto the further downstream device. Also in this case, the CPU controls totransmit the information signals in the orderly sequence thereof.

When the whole receiving interval times of a plurality of signals arestored to perform a delayed transmission according to the intervaltimes, the controls of the operations performed by the CPU may becomecomplicated and the size of the storage capacity for the operations mayincrease. However, by transmitting signals in a sequential manner asdescribed above, the controls may be simplified and the size of thestorage capacity may be reduced, but the interval times of theinformation signals in sending and those in receiving may becomedifferent. Even when the interval times of the information signals arechanged, it can be necessary to determine which signal corresponds towhich paper sheet or which paper sheet and thereafter.

On the contrary, as shown in the operations in the second exampleembodiment, if the transmission of the paper sheet forwarding signal andthe other information signals are kept in an orderly sequence thereof,it may be easy to connect the signals with the corresponding informationsignals, which can easily solve the above-described problem.

For example, the local sheet post-processing device may receive theinformation signals including the paper sheet information, then receivethe paper sheet forwarding signal, and confirm the contents of theinformation signals. When the paper sheet forwarding signal and theinformation signals are transmitted in the orderly sequence, the localsheet post-processing device can easily apply the paper sheetinformation included in the information signals to the paper sheetcorresponding to the paper sheet forwarding signal. At this time, theinformation signals may sequentially be transmitted immediately beforeor after the paper sheet forwarding signal has been transmitted, withoutchanging the sequence order of the paper sheet forwarding signal and theinformation signals. Therefore, the sheet post-processing operation canbe performed without making the operation control to be complex and thesize of the storage capacity to be increased.

When a plurality of stacks of paper sheets are conveyed in the localsheet post-processing device for the operations shown in FIGS. 12through 14, the CPU may perform parallel processing. Since the CPU ofthe local sheet post-processing device may take the operation proceduresfor the plurality of paper sheet stacks same as the operation proceduretaken for a single paper sheet as described above, the description ofthe detailed procedures is omitted.

Third Example Embodiment

Referring to a flowchart of FIG. 15, a communication procedure of anoperation of transmitting a leading edge discharging signal is describedaccording to a third example embodiment of the present invention.

The communication procedure of the operation according to the thirdexample embodiment is similar to the communication procedure of thesecond example embodiment. Except that the communication procedureperformed in the third example embodiment issues the leading edgedischarging signal as the paper sheet forwarding signal. Specifically,in the communication procedure according to the third example embodimentof the present invention, the leading edge discharging signal istransmitted from the communication unit of the upstream device to thecommunication unit of the local sheet post-processing device. Thecommunication unit of the local sheet post-processing device receivesthe leading edge discharging signal before or after the leading edge ofa paper sheet is discharged. The above-described transmission of theleading edge discharging signal can make the local sheet post-processingdevice recognize the timing of the leading edge of a paper sheet to beconveyed or fed. The other parts, structures, and functions are same asthose used in the first and second example embodiments. Therefore, thesame reference numbers as those used in the first and second exampleembodiment are given, and the description of these parts, structures,and functions are omitted in the third example embodiment.

In the flowchart of FIG. 15, the operation of transmitting the leadingedge discharging signal may be performed by the local sheetpost-processing device to receive and transmit the leading edgedischarging signal for informing the timing of conveying or feeding theleading edge of each paper sheet during the paper sheet feedingoperation.

When the leading edge of a paper sheet has come at a dischargingposition through which the paper sheet is discharged, for example, whenthe leading edge of a paper sheet is present at or in the vicinity ofthe pair of outlet rollers 11, the upstream device transmits the leadingedge discharging signal to the local sheet post-processing device.

In step S701, the CPU of the local sheet post-processing devicedetermines whether the local sheet post-processing device has receivedthe leading edge discharging signal. By receiving the leading edgedischarging signal, the local sheet post-processing device can recognizethe timing of conveyance of the paper sheet.

When the local sheet post-processing device has received the leadingedge discharging signal, the determination result in step S701 is YESand the process proceeds to step S702.

When the local sheet post-processing device has not yet received theleading edge discharging signal, the determination result in step S701is NO, and the process of step S701 repeats until the local sheetpost-processing device receives the leading edge discharging signal.

After the determination result in step S701 becomes “YES” by receivingthe leading edge discharging signal, the local sheet post-processingdevice can confirm various information requests or signals, determinewhich request or signal corresponds to which paper sheet or which papersheet and thereafter, and perform a paper sheet receiving operation, forexample, of rotating a sheet conveying motor, of moving the joggerfences 16 to a standby position according to its size, etc. in stepS702.

After step S702 is completed, the CPU of the local sheet post-processingdevice determines, in step S703, whether the leading edge of the papersheet has come at a discharging position, for example, whether theleading edge of a paper sheet is present at or in the vicinity of thepair of outlet rollers 11.

When the leading edge of the paper sheet is present at the dischargingposition, the determination in step S703 is YES, and the processproceeds to step S704.

When the leading edge of the paper sheet is not at the dischargingposition, the determination in step S703 is NO, and the process of stepS703 repeats until the leading edge of the paper sheet comes at thedischarging position.

In step S704, the CPU of the local sheet post-processing devicetransmits the leading edge discharging signal to the downstream device,and completes the procedure.

In a case in which a single paper sheet is fed to the local sheetpost-processing device, the local sheet post-processing device performsthe operation as shown in the flowchart of FIG. 15. That is, when theleading edge of the paper sheet has come at the discharging position, orwhen the leading edge of the paper sheet is present at or in thevicinity of the pair of outlet rollers 11, the CPU of the upstreamdevice transmits the leading edge discharging signal to the local sheetpost-processing device. By receiving the leading edge dischargingsignal, the local sheet post-processing device can recognize the timingof conveyance of the paper sheet.

In a case in which a plurality of paper sheets are fed to the localsheet post-processing device, the local sheet post-processing devicetemporarily writes the information signals including the paper sheetinformation, and transmits the information signals without changing thesequence order of the information signals with respect to the leadingedge discharging signal. The information signals are transmitted to thedownstream device at the timing immediately after the transmission ofthe leading edge discharging signal.

Specifically, when the plurality of paper sheets are continuously fed,the information signals received between the transmission of the leadingedge discharging signal of a first paper sheet or a paper sheet 1 andthe transmission of the leading edge discharging signal of a secondpaper sheet or a paper sheet 2 are collectively written or stored in onegroup unit as Group 1, and the information signals received between thetransmission of the leading edge discharging signal of the paper sheet 2and the transmission of the leading edge discharging signal of a papersheet 3 are collectively stored in one group unit as Group 2. Similarly,the information signals are stored respectively as Group 3, Group 4, andso on.

When the leading edge of the paper sheet 1 comes at the dischargingposition, the local sheet post-processing device transmits the leadingedge discharging signal to the downstream device. Immediately after thetransmission of the leading edge discharging signal, the local sheetpost-processing device transmits the information signals correspondingto Group 1. When the leading edge of the paper sheet 2 comes at thedischarging position, the local sheet post-processing device transmitsthe leading edge discharging signal to the downstream device, andimmediately transmits the information signals corresponding to Group 2.Similarly, the operation repeats for Group 3, Group 4, and so on.

The local sheet post-processing device temporarily writes theinformation signals including the paper sheet information, and transmitsthe leading edge discharging signal and the information signals withoutchanging the sequence order thereof. The information signals aretransmitted at the timing immediately after the transmission of theleading edge discharging signal.

The communication procedure that is taken when the plurality of papersheets are fed is basically same as the communication procedure in theflowchart of FIG. 15. The whole signals are transmitted without changingthe sequence order.

When the information signals and the leading edge discharging signal aretransmitted from the local sheet post-processing device, the downstreamdevice performs its operation in a same manner as the local sheetpost-processing device. That is, the downstream device temporarilywrites the information signals, and transmits the leading edgedischarging signal and the information signals to the further downstreamdevice.

In the second example embodiment of the present invention, each of thesheet post-processing devices 6 a, 6 b, 6 c, 6 d, and 6 e needs torecognize the timing of conveyance of a paper sheet. If the recognitionof the timing fails, it may be difficult to assuredly determine whichsignal corresponds to which paper sheet or which paper sheet andthereafter. Further, if the timing of conveyance of a paper sheet cannotproperly be recognized, the paper sheet receiving operation cannot beperformed at an appropriate timing. The paper sheet receiving operationmay include operations of rotating a sheet conveying motor, of movingthe jogger fences 16 to a standby position according to its size, etc.

According to the present example embodiment, the leading edgedischarging signal may be transmitted as the paper sheet forwardingsignal to the communication device of the downstream device at thetiming before or after the leading edge of the paper sheet isdischarged, and the downstream device can recognize the conveyance ofthe leading edge of the paper sheet by receiving the leading edgedischarging signal. Thereby, the uncertainty of the determination andthe inappropriateness of the timing can be reduced or prevented.

Fourth Example Embodiment

Referring to a flowchart of FIG. 16, a communication procedure of anoperation of a task of processing the paper sheet 1 is describedaccording to a fourth example embodiment of the present invention.

The communication procedure of the operation according to the fourthexample embodiment of the present invention is similar to thecommunication procedure of the third example embodiment. Except that thecommunication procedure performed by the fourth example embodimentwrites or stores a portion or whole set of the information signals as agroup unit. Further, in the fourth example embodiment, informationsignals can be transmitted by a flexible amount or length of bytethereof, from the upstream device to the downstream device during thepaper sheet feeding operation.

Specifically, in the communication procedure according to the fourthexample embodiment of the present invention, a portion or whole set ofthe information signals received between the transmission of the leadingedge discharging signal of a paper sheet 1 and the transmission of theleading edge discharging signal of a paper sheet 2 are collectivelywritten or stored in one group unit as Group 1, a portion or whole setof the information signals received between the transmission of theleading edge discharging signal of the paper sheet 2 and thetransmission of the leading edge discharging signal of a paper sheet 3are collectively written or stored in one group unit as Group 2.Similarly, the information signals are written or stored as Group 3,Group 4, and so on.

When the leading edge of the paper sheet 1 comes at the dischargingposition, the upstream device transmits the leading edge dischargingsignal to the downstream device. Immediately after the transmission ofthe leading edge discharging signal, the upstream device transmits theportion of whole set of the information signals corresponding to Group1. When the leading edge of the paper sheet 2 comes at the dischargingposition, the upstream device transmits the leading edge dischargingsignal to the downstream device, and immediately transmits the portionor whole set of the information signals corresponding to Group 2.Similarly, the operation repeats for Group 3, Group 4, and so on. Atthis time, the received signals including the leading edge dischargingsignal and the corresponding information signals are transmitted withoutchanging the sequence order thereof.

The other parts, structures, and functions are same as those used in thefirst and second example embodiments. Therefore, the same referencenumbers as those used in the first and second example embodiments aregiven, and the description of these parts, structures, and functions areomitted.

In the flowchart of FIG. 16, the task of processing the paper sheet 1,which is a first paper sheet of a stack of paper sheets, is describedaccording to the fourth example embodiment of the present invention.

In step S801, the CPU of the local sheet post-processing device, forexample, determines whether the local sheet post-processing device hasreceived the leading edge discharging signal of the paper sheet 1 fromthe upstream device.

When the local sheet post-processing device has received the leadingedge discharging signal of the paper sheet 1, the determination resultin step S801 is YES, and the process proceeds to step S802.

When the local sheet post-processing device has not yet received theleading edge discharging signal of the paper sheet 1, the determinationresult in step S801 is NO, and the process of step S801 repeats untilthe local sheet post-processing device receives the leading edgedischarging signal.

The CPU starts the task of the paper sheet 2, which is a second papersheet of the stack of paper sheets, in step S802, specifies the variable“A” representing the storage area A so as to assign the top address “a”thereto in step S803, and the process proceeds to step S804.

In step S804, the CPU determines whether the leading edge of the papersheet 1 has come at the discharging position, for example, whether theleading edge of the paper sheet is present at or in the vicinity of thepair of outlet rollers 11.

When the leading edge of the paper sheet 1 is present at the dischargingposition, the determination result in step S804 is YES, and the processproceeds to step S810.

When the leading edge of the paper sheet 1 is not present at thedischarging position, the determination result in step S804 is NO, andthe process proceeds to step S805.

In step S805, the CPU determines whether the local sheet post-processingdevice has received the leading edge discharging signal of the papersheet 2 from the upstream device.

When the local sheet post-processing device has received the leadingedge discharging signal of the paper sheet 2, the determination resultin step S805 is YES, and the process proceeds to step S809.

When the local sheet post-processing device has not yet received theleading edge discharging signal of the paper sheet 2, the determinationresult in step S805 is NO, and determines whether the local sheetpost-processing device has received a flexible amount of the informationsignals from the upstream device in step S806. The “information signals”in step S806 represents the various information signals that arereceived between the transmission of the leading edge discharging signalof the paper sheet 1 and the transmission of the leading edgedischarging signal of the paper sheet 2.

When the local sheet post-processing device has received a flexibleamount of the information signals, the determination result of step S806is YES, and the process proceeds to step S807.

When the local sheet post-processing device has not yet receivedinformation signals, the determination result of step S806 is NO, andthe process goes back to step S804. The CPU repeats the steps S804through S806 until the leading edge of the paper sheet 1 comes at thedischarging position or the local sheet post-processing device receivesthe leading edge discharging signal or a flexible amount of theinformation signals.

After the determination result in step S806 becomes “YES”, the CPUtemporarily writes the received information signals by the number ofaddresses “N” corresponding to the flexible amount of the informationsignals in Group 1, starting from the top address “a” in the storingarea A, in step S807. The CPU then increments the variable “A” by thenumber of addresses “N” according to the flexible amount of theinformation signals in step S808, and the process goes back to stepS804. The CPU repeats steps S804 through S808 until no more sequentialinformation signals for Group 1 is transmitted.

After the determination result in step S805 becomes “YES”, the CPUdetermines whether the leading edge of the paper sheet 2 has come at thedischarging position in step S809.

When the leading edge of the paper sheet 2 has come at the dischargingposition, the determination result in step S809 is YES, and the processproceeds to step S810.

When the leading edge of the paper sheet 2 has not yet come at thedischarging position, the determination result in step S809 is NO, andthe process of step S809 repeats until the leading edge of the papersheet 2 comes at the discharging position.

After the arrival of the leading edge of the paper sheet 2 at thedischarging position is confirmed in step S809, the CPU transmits theleading edge discharging signal to the downstream device in step S810,and determines whether the received information signals still remain inthe storing unit of the local sheet post-processing device in step S811.

When the received information signals still remain in the storing unit,the determination result in step S811 is YES, and the process proceedsto step S812.

When the received information signals have completely transmitted and noinformation signals remain in there, the determination result in stepS811 is NO, and the CPU terminates the process.

After the determination result in step S811 becomes “YES”, the CPUassigns the top address “a” to the variable “A” in step S812, and readsout and transmits the received information signals in Group 1, startingfrom the top address “a” to the downstream device in step S813. The CPUthen increments the variable “A” by one in step S814, and the processproceeds to step S815.

In step S815, the CPU determines whether the local sheet post-processingdevice has completed the transmission of the information signals ofGroup 1 with respect to the downstream device.

When the local sheet post-processing device has completed thetransmission of the information signals of Group 1, the determinationresult in step S815 is YES, and the CPU terminates the sheetpost-processing operation in the local sheet post-processing device.

When the local sheet post-processing device still has the informationsignals to be transmitted to the downstream device, the determinationresult in step S815 is NO, and the process goes back to step S813 so asto repeat steps S813 through S815 until no more sequential informationsignal to be transmitted for the corresponding paper sheet remains inthe storing area A of the storing unit of the local sheetpost-processing device.

Referring to flowcharts of FIGS. 17A and 17B, respective communicationprocedures of tasks of paper sheets 2 and 3, which are second and thirdpaper sheets of the stack of paper sheets, respectively, are describedaccording to the fourth example embodiment of the present invention.

The communication procedures of the flowcharts shown in FIGS. 17A and17B are basically similar to the communication procedure of theflowchart shown in FIG. 16. Except, the CPU starts the task of the papersheet 3 in step S902 of the flowchart of FIG. 17A, and starts the taskof a paper sheet 4 in step S902 of the flowchart of FIG. 17B. Further, astoring area B including the top address “b” and a variable “B” isapplied in the communication procedure shown in FIG. 17A, and a storingarea C including the top address “c” and a variable “C” is applied inthe communication procedure shown in FIG. 17B.

Here, the communication procedures of the respective tasks of the papersheets 2 and 3 are described. Since the communication procedures of therespective tasks of the paper sheet 2 and 3 are basically similar toeach other, the description of the communication procedure of the taskof the paper sheet 3 is additionally generated to the description of thecommunication procedure of the task of the paper sheet 2.

In step S901, the CPU of the local sheet post-processing devicedetermines whether the local sheet post-processing device has receivedthe leading edge discharging signal of the paper sheet 2 (the papersheet 3 in FIG. 17B) from the upstream device.

When the local sheet post-processing device has received the leadingedge discharging signal of the paper sheet 2 (or the paper sheet 3), thedetermination result in step S901 is YES, and the process proceeds tostep S902.

When the local sheet post-processing device has not yet received theleading edge discharging signal of the paper sheet 2 (or the paper sheet3), the determination result in step S901 is NO, and the process of stepS901 repeats until the local sheet post-processing device receives theleading edge discharging signal of the paper sheet 2 (or the paper sheet3).

The CPU starts the task of the paper sheet 3 in step S902 (the task ofthe paper sheet 4 in FIG. 17B). The CPU then specifies the variable “B”(the variable “C” in FIG. 17B) representing the storage area B (thestoring area C in FIG. 17B) so as to assign the top address “b” (the topaddress “c” in FIG. 17B) thereto in step S903, and the process proceedsto step S904.

In step S904, the CPU determines whether the leading edge of the papersheet 2 (the leading edge of the paper sheet 3 in FIG. 17B) has come atthe discharging position, for example, whether the leading edge of thepaper sheet is present at or in the vicinity of the pair of outletrollers 11.

When the leading edge of the paper sheet 2 (or the paper sheet 3) ispresent at the discharging position, the determination result in stepS904 is YES, and the process proceeds to step S910.

When the leading edge of the paper sheet 2 (or the paper sheet 3) is notat the discharging position, the determination result in step S904 isNO, and the process proceeds to step S905.

In step S905, the CPU determines whether the local sheet post-processingdevice has received the leading edge discharging signal of the papersheet 3 (or the paper sheet 4) from the upstream device.

When the local sheet post-processing device has received the leadingedge discharging signal of the paper sheet 3 (or the paper sheet 4), thedetermination result in step S905 is YES, and the process proceeds tostep S909.

When the local sheet post-processing device has not yet received theleading edge discharging signal of the paper sheet 3 (or the paper sheet4), the determination result in step S905 is NO, and determines whetherthe local sheet post-processing device has received a flexible amount ofthe information signals from the upstream device. The “informationsignals” in step S906 represents the various information signals thatare received between the transmission of the leading edge dischargingsignal of the paper sheet 2 and the transmission of the leading edgedischarging signal of the paper sheet 3. In step S906 in FIG. 17B, theinformation signals represents the various information signals that arereceived between the transmission of the leading edge discharging signalof the paper sheet 3 and the transmission of the leading edgedischarging signal of the paper sheet 4.

When the local sheet post-processing device has received a flexibleamount of the information signals, the determination result of step S906is YES, and the process proceeds to step S907.

When the local sheet post-processing device has not yet received theinformation signals, the determination result of step S906 is NO, andthe process goes back to step S904. The CPU repeats steps S904 throughS906 until the local sheet post-processing device receives the leadingedge discharging signal or a flexible amount of the information signals.

After the determination result in step S906 becomes “YES”, the CPUtemporarily writes the received information signals by the number ofaddresses “N” corresponding to the flexible amount of the informationsignals in Group 2 (Group 3 in FIG. 17B), starting from the top address“b” (or the top address “c”) in the storing area B (or the storing areaC) in step S907. The CPU then increments the variable “B” (the variable“C” in FIG. 17B) by the number of addresses “N” according to theflexible amount of the information signals in step S908, and the processgoes back to step S904. The CPU repeats steps S804 through S808 until nomore sequential information signals for Group 2 (or Group 3) istransmitted.

After the determination result in step S905 becomes “YES”, the CPUdetermines whether the leading edge of the paper sheet 3 (or the leadingedge of the paper sheet 4 in FIG. 17B) has come at the dischargingposition in step S909.

When the leading edge of the paper sheet 3 (or the paper sheet 4) hascome at the discharging position, the determination result in step S909is YES, and the process proceeds to step S910.

When the leading edge of the paper sheet 3 (or the paper sheet 4) hasnot yet come at the discharging position, the determination result instep S909 is NO, and the process of step S909 repeats until the leadingedge of the paper sheet 3 (or the paper sheet 4) comes at thedischarging position.

After the arrival of the leading edge of the paper sheet 3 (the leadingedge of the paper sheet 4 in FIG. 17B) at the discharging position isconfirmed in step S909, the CPU transmits the leading edge dischargingsignal to the downstream device in step S910, and determines whether thereceived information signals still remain in the storing unit of thelocal sheet post-processing device in step S911.

When the received information signals still remain in the storing unit,the determination result in step S911 is YES, and the process proceedsto step S912.

When the received information signals have completely transmitted and noinformation signals remain in there, the determination result in stepS911 is NO, and the CPU terminates the process.

After the determination result in step S911 becomes “YES”, the CPUassigns the top address “b” to the variable “B” (or the top address “c”to the variable “C” in FIG. 17B) in step S912, and reads out andtransmits the received information signals in Group 2 (or Group 3),starting from the top address “b” (or the top address “c”) to thedownstream device in step S913. The CPU then increments the variable “B”(or the variable “C”) by one in step S914, and the process proceeds tostep S915.

In step S915, the CPU determines whether the local sheet post-processingdevice has completed the transmission of the information signals ofGroup 2 (or Group 2) with respect to the downstream device.

When the local sheet post-processing device has completed thetransmission of the information signals of Group 2 (or Group 3), thedetermination result in step S915 is YES, and the CPU terminates thesheet post-processing operation in the local sheet post-processingdevice.

When the local sheet post-processing device still has the informationsignals to be transmitted to the downstream device, the determinationresult in step S915 is NO, and the process goes back to step S913 so asto repeat steps S913 through S915 until no more sequential informationsignal to be transmitted for the corresponding paper sheet remains inthe storing area B (or the storing area C) of the storing unit of thelocal sheet post-processing device.

In a case in which the information signals are transmitted immediatelybefore the leading edge discharging signal in the third exampleembodiment, the timing of transmission of the leading edge dischargingsignal may delay according to the number or amount of the informationsignals. When serial communication, for example the UART, is selectedfor transmission, the delay of the timing of transmitting the lastleading edge discharging signal may greatly depend on the number oramount of the information signals.

When the upstream device has a delay of the timing of transmitting thelast leading edge discharging signal as described above, the downstreamdevice controlled to start driving its conveying motor depending uponthe receipt of the leading edge discharging signal may cause a delay tostart the conveying motors, which can cause deterioration in performanceof conveying paper sheets.

Transmission of the information signals immediately before the leadingedge discharging signal may cause a sheet post-processing device to makethe interval between the receipt of the information signals and thetransmission thereof to be the longest interval. That is, the sheetpost-processing device may cause a delay in transferring the signal tothe downstream sheet post-processing device, which cannot make it toprepare the paper sheet receiving operation depending on therequirements of the signal.

In contrast, the sheet post-processing devices in the present exampleembodiment can:

1) Reduce if not prevent the delay of transmitting the leading edgedischarging signal depending on the number or amount of the informationsignals;

2) Reduce if not prevent the delay of starting the conveying motor whenthe downstream device is controlled to drive the conveying motor inresponse to the receipt of the leading edge discharging signal and tosecure an appropriate level of the performance in the paper sheetfeeding operation; and

3) Prepare the paper sheet receiving operation in a proper mannerwithout causing the delay in transferring the signal to the downstreamdevice.

Fifth Example Embodiment

Referring to flowcharts of FIGS. 18 and 19, communication procedures ofrespective tasks of processing the leading and trailing edges of a papersheet are described according to a fifth example embodiment of thepresent invention.

The communication procedures of the tasks according to the fifth exampleembodiment are similar to the communication procedure of the secondexample embodiment. Except that the communication procedure performed inthe fifth example embodiment issues, in addition to the leading edgedischarging signal, the trailing edge discharging signal also as thepaper sheet forwarding signal. Specifically, in the communicationprocedures in the flowcharts of FIGS. 18 and 19 according to the fifthexample embodiment of the present invention, the leading edgedischarging signal is transmitted from the communication unit of theupstream device to the communication unit of the local sheetpost-processing device before or after the leading edge of a paper sheetis discharged, and the trailing edge discharging signal is transmittedfrom the communication unit of the upstream device to the communicationunit of the local sheet post-processing device before or after thetrailing edge of a paper sheet is discharged. The above-describedtransmissions of the leading edge discharging signal and the trailingedge discharging signal can make the local sheet post-processing devicerecognize the respective timings of the leading and trailing edges of apaper sheet to be conveyed or fed, respectively. The other parts,structures, and functions are same as those used in the first and secondexample embodiments. Therefore, the same reference numbers as those usedin the first and second example embodiment are given, and thedescription of these parts, structures, and functions are omitted in thefifth example embodiment.

As previously described, in the fifth example embodiment, two kinds ofthe paper sheet forwarding signal are provided. That is, the leadingedge discharging signal is used to inform the timing of conveying theleading edge of a paper sheet, and the trailing edge discharging signalis used to inform the timing of conveying the trailing edge of the papersheet.

The flowchart of FIG. 18 shows the task of processing the leading edgeof a paper sheet, and the flowchart of FIG. 19 shows the task ofprocessing the trailing edge of a paper sheet.

When the leading edge of a paper sheet has come at a dischargingposition through which the paper sheet is discharged, for example, whenthe leading edge of a paper sheet is present at or in the vicinity ofthe pair of outlet rollers 11, the upstream device transmits the leadingedge discharging signal to the local sheet post-processing device. Byreceiving the leading edge discharging signal, the local sheetpost-processing device can recognize the timing of the leading edge ofthe paper sheet to be discharged.

According to the receipt of the leading edge discharging signal, thelocal sheet post-processing device can confirm various informationrequests or signals, determine which request or signal corresponds towhich paper sheet or which paper sheet and thereafter, and perform apaper sheet receiving operation, for example, of rotating a sheetconveying motor, of moving the jogger fences 16 to a standby positionaccording to its size, etc.

When the trailing edge of the paper sheet has come at a dischargingposition through which the paper sheet is discharged, for example, whenthe trailing edge of the paper sheet is present at or in the vicinity ofthe pair of outlet rollers 11, the upstream device transmits thetrailing edge discharging signal to the local sheet post-processingdevice. By receiving the trailing edge discharging signal, the localsheet post-processing device can recognize the timing of the trailingedge of the paper sheet to be discharged. For example, even when thelength of a paper sheet is not informed, the local sheet post-processingdevice can determine whether a paper jam has occurred if the trailingedge discharging signal is received.

Similar to the operation performed by the local sheet post-processingdevice, when the leading edge of a paper sheet has come at thedischarging position through which the paper sheet is discharged, forexample, when the leading edge of a paper sheet is present at or in thevicinity of the pair of outlet rollers 11, the downstream devicetransmits the leading edge discharging signal to the further downstreamdevice. And, when the trailing edge of the paper sheet has come at thedischarging position, for example, when the trailing edge of the papersheet is present at or in the vicinity of the pair of outlet rollers 11,the downstream device transmits the trailing edge discharging signal tothe further downstream device.

In step S1001 of the flowchart of FIG. 18, the CPU of the local sheetpost-processing device determines whether the local sheetpost-processing device has received the leading edge discharging signalfrom the upstream device.

When the local sheet post-processing device has received the leadingedge discharging signal, the determination result in step S1001 is YES,and the process proceeds to step S1002.

When the local sheet post-processing device has not yet received theleading edge discharging signal, the determination result in step S1001is NO, and the process repeats until the local sheet post-processingdevice receives the leading edge discharging signal.

The CPU starts the task of processing the trailing edge of the papersheet in step S1002, starts the paper sheet receiving operation in stepS1003, and determines whether the leading edge of the paper sheet hascome at the discharging position in step S1004.

When the leading edge of the paper sheet is present at the dischargingposition, the determination result in step S1004 is YES, and the processproceeds to step S1005.

When the leading edge of the paper sheet is not present at thedischarging position, the determination result in step S1004 is NO, andthe process of step S1004 repeats until the leading edge of the papersheet comes at the discharging position.

After the determination result in step S1004 becomes “YES”, the CPUtransmits the leading edge discharging signal to the downstream devicein step S1005, and terminates the process.

In step S1101 of the flowchart of FIG. 19, the CPU of the local sheetpost-processing device determines whether the local sheetpost-processing device has received the trailing edge discharging signalfrom the upstream device.

When the local sheet post-processing device has received the trailingedge discharging signal, the determination result in step S1101 is YES,and the process proceeds to step S1102.

When the local sheet post-processing device has not yet received thetrailing edge discharging signal, the determination result in step S1101is NO, and the process of step S1101 repeats until the local sheetpost-processing device receives the trailing edge discharging signal.

The CPU starts the trailing edge receiving operation in step S1102, anddetermines whether the trailing edge of the paper sheet has come at thedischarging position in step S1103.

When the trailing edge of the paper sheet is present at the dischargingposition, the determination result in step S1103 is YES, and the processproceeds to step S1104.

When the trailing edge of the paper sheet is not present at thedischarging position, the determination result in step S1103 is NO, andthe process of step S1103 repeats until the trailing edge of the papersheet comes at the discharging position.

After the determination result in step S1103 becomes “YES”, the CPU ofthe local sheet post-processing device transmits the trailing edgedischarging signal to the downstream device, and completes the process.

The transmission timings of the commands or signals used for theabove-described flowcharts of FIGS. 18 and 19 are shown in a schematicdiagram of FIG. 20.

As shown in the diagram of FIG. 20, the leading edge discharging signalsthat are indicated as “S1” and “S3” and the trailing edge dischargingsignal that is indicated as “S2” remain in a standby mode while thesesignals S1, S2, and S3 are transmitted from a device 1 representing anupstream device to a device 2 representing a local sheet post-processingdevice, and from the device 2 to a device 3 representing a downstreamdevice.

In the operations of the second example embodiment in the flowchart ofFIG. 14, each of the sheet post-processing devices 6 a, 6 b, 6 c, 6 d,and 6 e needs to recognize the timing of conveyance of a paper sheet.

If the recognition of the timing fails, it may be difficult to assuredlydetermine which request or signal corresponds to which paper sheet orwhich paper sheet and thereafter. Further, if the timing of conveyanceof a paper sheet cannot properly be recognized, the downstream devicecannot perform the paper sheet receiving operation at an appropriatetiming, as previously described.

Further, when the length of the paper sheet is not informed, thedownstream device needs to recognize the timing of receiving thetrailing edge of the paper sheet so as to detect a defect, for example apaper jam. When the timing cannot specifically be recognized, thedownstream device may fail to determine the detection of the paper jamand so forth.

The communication procedure performed in the fifth example embodiment,therefore, uses both the leading edge discharging signal and thetrailing edge discharging signal as the paper sheet forwarding signalthat are transmitted before or after the leading and trailing edges of apaper sheet are discharged, respectively. With the above-describedtransmissions of the leading edge discharging signal and the trailingedge discharging signal, the downstream device can recognize theconveyance or passage of the leading and trailing edges of a papersheet, respectively.

With the above-described operation, the present example embodiment can:

1) Correctly determine which request or signal corresponds to whichpaper sheet or which paper sheet and thereafter;

2) Clearly recognize the timing of conveyance of a paper sheet so thatthe downstream device can perform the paper sheet receiving operation,for example, of rotating the sheet conveying motor, of moving the joggerfences 16 to the standby position according to its size, etc. atrespective appropriate timings; and

3) Correctly recognize the timing of conveyance of the trailing edge ofa paper sheet so that the downstream device can easily determine whethera paper jam has occurred, which can avoid the occurrence of paper jam.

Sixth Example Embodiment

Referring to flowcharts of FIGS. 21, 22, 23A, and 23B, communicationprocedures of tasks of processing the leading and trailing edges ofpaper sheets 1 and 2 are described according to examples of a sixthexample embodiment of the present invention.

The communication procedures of the tasks according to the sixth exampleembodiment of the present invention are similar to the communicationprocedures of the fifth example embodiment. Except that each of thecommunication procedures performed by the sixth example embodimentstores a portion or whole set of the information signals as a group.

Specifically, in the communication procedures according to the sixthexample embodiment of the present invention, a portion or whole set ofthe information signals received between the transmission of the leadingedge discharging signal of a paper sheet 1 and the transmission of thetrailing edge discharging signal of the paper sheet 1 are collectivelywritten or stored in one group unit as Group 1-1 as shown in FIG. 21, aportion or whole set of the information signals received between thetransmission of the trailing edge discharging signal of the paper sheet1 and the transmission of the leading edge discharging signal of a papersheet 2 are collectively written or stored in one group unit as Group1-2 as shown in FIG. 22. Similarly, the information signals are writtenor stored as Group 2-1 in FIG. 23A, Group 2-2 in FIG. 23B, and so on.

When the leading edge of the paper sheet 1 comes at the dischargingposition, the upstream device transmits the leading edge dischargingsignal to the downstream device. Immediately after the transmission ofthe leading edge discharging signal, the upstream device transmits theportion of whole set of the information signals corresponding to Group1-1. When the trailing edge of the paper sheet 1 comes at thedischarging position, the upstream device transmits the trailing edgedischarging signal to the downstream device, and immediately transmitsthe portion or whole set of the information signals corresponding toGroup 1-2. Similarly, the operation repeats for Group 2-1, Group 2-2,and so on. At this time, the received signals including the leading edgedischarging signals, the trailing edge discharging signals, and thecorresponding information signals are transmitted without changing thesequence order thereof.

The other parts, structures, and functions are same as those used in thefirst, second and fifth example embodiments. Therefore, the samereference numbers as those used in the first, second and fifth exampleembodiments are given, and the description of these parts, structures,and functions are omitted.

In the flowcharts of FIGS. 21, 22, 23A, and 23B, respectivecommunication procedures to send and receive signals during the papersheet feeding operations are described as the examples of the sixthexample embodiment of the present invention.

As previously described in the fifth example embodiment, when theleading edge of a paper sheet has come at a discharging position throughwhich the paper sheet is discharged, for example, when the leading edgeof a paper sheet is present at or in the vicinity of the pair of outletrollers 11, the upstream device transmits the leading edge dischargingsignal to the local sheet post-processing device. By receiving theleading edge discharging signal, the local sheet post-processing devicecan recognize the timing of conveyance of the leading edge of the papersheet.

Further, when the trailing edge of a paper sheet has come at adischarging position through which the paper sheet is discharged, forexample, when the trailing edge of a paper sheet is present at or in thevicinity of the pair of outlet rollers 11, the upstream device transmitsthe trailing edge discharging signal to the local sheet post-processingdevice. By receiving the trailing edge discharging signal, the localsheet post-processing device can recognize the timing of conveyance ofthe trailing edge of the paper sheet.

In the sixth example embodiment, the local sheet post-processing devicetemporarily writes or stores the information signals includinginformation of the size, thickness, and ID of the paper sheets, therequest of the sheet post-processing operation, and so forth, andtransmits the information signals without changing the sequence orderthereof with respect to the leading edge discharging signal and thetrailing edge discharging signal. The information signals aretransmitted at the timing immediately after the transmission of theleading edge discharging signal or immediately after the transmission ofthe trailing edge discharging signal, depending on the dischargingsignal to which the information signals correspond.

As previously described, when the plurality of paper sheets arecontinuously fed, the respective information signals received betweenthe transmissions of two adjacent discharging signals are collectivelywritten or stored into the corresponding groups.

The upstream device transmits the leading edge discharging signal to thedownstream device when the leading edge of the paper sheet 1 comes atthe discharging position, then immediately transmits the informationsignals corresponding to Group 1-1.

The upstream device transmits the trailing edge discharging signal tothe downstream device when the trailing edge of the paper sheet 1 comesat the discharging position, then immediately transmits the informationsignals corresponding to Group 1-2.

Similarly, when the leading edge of the paper sheet 2 comes at thedischarging position, the upstream device transmits the leading edgedischarging signal to the downstream device, then immediately transmitsthe information signals corresponding to Group 2-1. Further, when thetrailing edge of the paper sheet 2 comes at the discharging position,the upstream device transmits the trailing edge discharging signal tothe downstream device, then immediately transmits the informationsignals corresponding to Group 2-2. Similarly, the operation repeats forGroup 3-1, Group 3-2, and so on.

Each sheet post-processing device temporarily stores the informationsignals, and transmits the leading edge discharging signal, the trailingedge discharging signal, and the information signals without changingthe sequence order thereof. The information signals are transmitted atthe timing immediately after the transmission of the leading edgedischarging signal or immediately after the transmission of the trailingedge discharging signal.

The communication procedure that is taken when the plurality of papersheets are fed is basically same as the communication procedure asdescribed above. The signals are transmitted without changing thesequence order thereof.

When the leading edge discharging signal, the trailing edge dischargingsignal, and the information signals are transmitted from the local sheetpost-processing device, the downstream device performs in a same manneras the local sheet post-processing device. That is, the downstreamdevice temporarily writes the information signals, and transmits theleading edge discharging signal, the trailing edge discharging signal,and the information signals to the further downstream device.

In the flowchart of FIG. 21, the communication procedure of the task ofprocessing the leading edge of the paper sheet 1 is described accordingto the sixth example embodiment of the present invention.

In step S1201, the CPU of the local sheet post-processing device, forexample, determines whether the local sheet post-processing device hasreceived the leading edge discharging signal of the paper sheet 1 fromthe upstream device.

When the local sheet post-processing device has received the leadingedge discharging signal of the paper sheet 1, the determination resultin step S1201 is YES, and the process proceeds to step S1202.

When the local sheet post-processing device has not yet received theleading edge discharging signal of the paper sheet 1, the determinationresult in step S1201 is NO, and the process of step S1201 repeats untilthe local sheet post-processing device receives the leading edgedischarging signal of the paper sheet 1.

The CPU starts the task of processing the trailing edge of the papersheet 1 in step S1202, specifies the variable “A” representing thestorage area A so as to assign the top address “a” thereto in stepS1203, and the process proceeds to step S1204.

In step S1204, the CPU determines whether the leading edge of the papersheet 1 has come at the discharging position.

When the leading edge of the paper sheet 1 is present at the dischargingposition, the determination result in step S1204 is YES, and the processproceeds to step S1210.

When the leading edge of the paper sheet 1 is not present at thedischarging position, the determination result in step S1204 is NO, andthe process proceeds to step S1205.

In step S1205, the CPU determines whether the local sheetpost-processing device has received the trailing edge discharging signalof the paper sheet 1 from the upstream device.

When the local sheet post-processing device has received the trailingedge discharging signal of the paper sheet 1, the determination resultin step S1205 is YES, and the process proceeds to step S1209.

When the local sheet post-processing device has not yet received thetrailing edge discharging signal of the paper sheet 1, the determinationresult in step S1205 is NO, and determines whether the local sheetpost-processing device has received a flexible amount of the informationsignals from the upstream device in step S1206. The “informationsignals” in step S1206 represents the various information signals thatare received between the transmission of the leading edge dischargingsignal of the paper sheet 1 and the transmission of the trailing edgedischarging signal of the paper sheet 1. In this case, each informationsignal may be transmitted not in a given or fixed amount but in aflexible amount thereof. That is, the length of byte of the address(referred to as “N”) to be used may be longer than the length used forwriting and storing the fixed amount of the information signals.

When the local sheet post-processing device has received a flexibleamount of the information signals, the determination result of stepS1206 is YES, and the process proceeds to step S1207.

When the local sheet post-processing device has not yet receivedinformation signals, the determination result of step S1206 is NO, andthe process goes back to step S1204. The CPU repeats steps S1204 throughS1206 until the leading edge of the paper sheet 1 comes at thedischarging position or the local sheet post-processing device receivesthe trailing edge discharging signal or a flexible amount of theinformation signals.

After the determination result in step S1206 has become “YES”, the CPUtemporarily writes the received information signal by the number ofaddresses “N” corresponding to the flexible amount of informationsignals in Group 1-1, starting from the top address “a” in the storingarea A, in step S1207. The CPU then increments the variable “A” by thenumber of addresses “N” according to the flexible amount of theinformation signals in step S1208, and the process goes back to stepS1204. The CPU repeats steps S1204 through S1208 until no moresequential information signals for Group 1-1 is transmitted.

After the determination result in step S1205 becomes “YES”, the CPUdetermines whether the leading edge of the paper sheet 1 has come at thedischarging position in step S1209.

When the leading edge of the paper sheet 1 has come at the dischargingposition, the determination result in step S1209 is YES, and the processproceeds to step S1210.

When the leading edge of the paper sheet 1 has not yet come at thedischarging position, the determination result in step S1209 is NO, andthe process of step S1209 repeats until the leading edge of the papersheet 1 comes at the discharging position.

After the arrival of the leading edge of the paper sheet 1 at thedischarging position is confirmed in step S1209, the CPU transmits theleading edge discharging signal to the downstream device in step S1210,and determines whether the received information signals still remain inthe storing unit of the local sheet post-processing device in stepS1211.

When the received information signals still remain in the storing unit,the determination result in step S1211 is YES, and the process proceedsto step S1212.

When the received information signals have completely transmitted and noinformation signals remain in there, the determination result in stepS1211 is NO, and the CPU terminates the process.

After the determination result in step S1211 becomes “YES”, the CPUassigns the top address “a” to the variable “A” in step S1212, reads outand transmits the received information signals in Group 1-1, startingfrom the top address “a” to the downstream device in step S1213. The CPUthen increments the variable “A” by one in step S1214, and the processproceeds to step S1215.

In step S1215, the CPU determines whether the local sheetpost-processing device has completed the transmission of the informationsignals of Group 1-1 with respect to the downstream device.

When the local sheet post-processing device has completed thetransmission of the information signals of Group 1-1, the determinationresult in step S1215 is YES, and the CPU terminates the sheetpost-processing operation in the local sheet post-processing device.

When the local sheet post-processing device still has the informationsignals to be transmitted to the downstream device, the determinationresult in step S1215 is NO, and the process goes back to step S1213 soas to repeat steps S1213 through S1215 until no more sequentialinformation signal of Group 1-1 to be transmitted for the correspondingpaper sheet remains in the storing area A of the storing unit of thelocal sheet post-processing device.

In the flowchart shown in FIG. 22, the communication procedure of thetask of processing the trailing edge of the paper sheet 1 is describedas another example of the sixth example embodiment of the presentinvention.

In step S1301, the CPU of the local sheet post-processing devicedetermines whether the local sheet post-processing device has receivedthe trailing edge discharging signal of the paper sheet 1 from theupstream device.

When the local sheet post-processing device has received the trailingedge discharging signal of the paper sheet 1, the determination resultin step S1301 is YES, and the process proceeds to step S1302.

When the local sheet post-processing device has not yet received thetrailing edge discharging signal of the paper sheet 1, the determinationresult in step S1301 is NO, and the process of step S1301 repeats untilthe local sheet post-processing device receives the trailing edgedischarging signal of the paper sheet 1.

The CPU starts the task of processing the leading edge of the papersheet 2 in step S1302, specifies the variable “A′” representing thestorage area A′ so as to assign the top address “a′” thereto in stepS1303, and the process proceeds to step S1304.

In step S1304, the CPU determines whether the trailing edge of the papersheet 1 has come at the discharging position.

When the trailing edge of the paper sheet 1 is present at thedischarging position, the determination result in step S1304 is YES, andthe process proceeds to step S1310.

When the trailing edge of the paper sheet 1 is not present at thedischarging position, the determination result in step S1304 is NO, andthe process proceeds to step S1305.

In step S1305, the CPU determines whether the local sheetpost-processing device has received the leading edge discharging signalof the paper sheet 2 from the upstream device.

When the local sheet post-processing device has received the leadingedge discharging signal of the paper sheet 2, the determination resultin step S1305 is YES, and the process proceeds to step S1309.

When the local sheet post-processing device has not yet received theleading edge discharging signal of the paper sheet 2, the determinationresult in step S1305 is NO, and determines whether the local sheetpost-processing device has received a flexible amount of the informationsignals from the upstream device. The “information signals” in stepS1306 represents the various information signals that are receivedbetween the transmission of the trailing edge discharging signal of thepaper sheet 1 and the transmission of the leading edge dischargingsignal of the paper sheet 2. In this case, each information signal maybe transmitted not in a fixed amount but in a flexible amount thereof.That is, the length of byte of the address (referred to as “N”) to beused may be longer than the length used for writing and storing thefixed amount of the information signals.

When the local sheet post-processing device has received a flexibleamount of the information signals, the determination result of stepS1306 is YES, and the process proceeds to step S1307.

When the local sheet post-processing device has not yet receivedinformation signals, the determination result of step S1306 is NO, andthe process goes back to step S1304. The CPU repeats steps S1304 throughS1306 until the trailing edge of the paper sheet 1 comes at thedischarging position or the local sheet post-processing device receivesthe leading edge discharging signal of the paper sheet 2 or a flexibleamount of the information signals.

After the determination result in step S1306 becomes “YES”, the CPUtemporarily writes the received information signal by the number ofaddresses “N” corresponding to the flexible amount of informationsignals in Group 1-2, starting from the top address “a′” in the storingarea A′, in step S1307. The CPU then increments the variable “A′” by thenumber of addresses “N” according to the flexible amount of theinformation signals in step S1308, and the process goes back to stepS1304. The CPU repeats steps S1304 through S1308 until no moresequential information signals for Group 1-2 is transmitted.

After the determination result in step S1305 becomes “YES”, the CPUdetermines whether the trailing edge of the paper sheet 1 has come atthe discharging position in step S1309.

When the trailing edge of the paper sheet 1 is present at thedischarging position, the determination result in step S1309 is YES, andthe process proceeds to step S1310.

When the trailing edge of the paper sheet 1 is not yet at thedischarging position, the determination result in step S1309 is NO, andthe process of step S1309 repeats until the trailing edge of the papersheet 1 comes at the discharging position.

After the arrival of the trailing edge of the paper sheet 1 at thedischarging position is confirmed in step S1309, the CPU transmits thetrailing edge discharging signal to the downstream device in step S1310,and determines whether the received information signals still remain inthe storing unit of the local sheet post-processing device in stepS1311.

When the received information signals still remain in the storing unit,the determination result in step S1311 is YES, and the process proceedsto step S1312.

When the received information signals have completely transmitted and noinformation signals remain in there, the determination result in stepS1311 is NO, and the CPU terminates the process.

After the determination result in step S1311 becomes “YES”, the CPUassigns the top address “a′” to the variable “A′” in step S1312, readsout and transmits the received information signals in Group 1-2,starting from the top address “a′” to the downstream device in stepS1313. The CPU then increments the variable “A′” by one in step S1314,and the process proceeds to step S1315.

In step S1315, the CPU determines whether the local sheetpost-processing device has completed the transmission of the informationsignals of Group 1-2 with respect to the downstream device.

When the local sheet post-processing device has completed thetransmission of the information signals of Group 1-2, the determinationresult in step S1315 is YES, and the CPU terminates the sheetpost-processing operation in the local sheet post-processing device.

When the local sheet post-processing device still has the informationsignals to be transmitted to the downstream device, the determinationresult in step S1315 is NO, and the process goes back to step S1313 soas to repeat steps S1313 through S1315 until no more sequentialinformation signal of Group 1-2 to be transmitted for the correspondingpaper sheet remains in the storing area A′ of the storing unit of thelocal sheet post-processing device.

In the flowcharts of FIGS. 23A and 23B, the respective procedures of thetasks of processing the leading and trailing edges of the paper sheet 2are described according to other examples of the sixth exampleembodiment of the present invention.

The communication procedures of the flowcharts shown in FIGS. 23A and23B are basically similar to the procedures of the flowcharts shown inFIGS. 21 and 22, respectively. Except, the CPU starts the task of thetrailing edge of the paper sheet 2 in step S1402 of the flowchart ofFIG. 23A, and starts the task of the leading edge of the paper sheet 3in step S1402 of the flowchart of FIG. 23B. Further, a storing area Bincluding the top address “b” and a variable “B” is applied in thecommunication procedures shown in the flowchart of FIG. 23A, and astoring area B′ including the top address “b′” and a variable “B′” isapplied in the communication procedures shown in the flowchart of FIG.23B.

Here, the communication procedures of the respective tasks of theleading and trailing edges of the paper sheet 2 are described. Since thecommunication procedures of the respective tasks of the leading andtrailing edges of the paper sheet 2 are basically similar to each other,the description of the communication procedure of the task of thetrailing edge of the paper sheet 2 is additionally generated to thedescription of the communication procedure of the task of the leadingedge of the paper sheet 2.

In step S1401, the CPU of the local sheet post-processing devicedetermines whether the local sheet post-processing device has receivedthe leading edge discharging signal of the paper sheet 2 (the trailingedge of the paper sheet 2 in FIG. 23B) from the upstream device.

When the local sheet post-processing device has received the leadingedge discharging signal of the paper sheet 2 (or the trailing edgedischarging signal of the paper sheet 2), the determination result instep S1401 is YES, and the process proceeds to step S1402.

When the local sheet post-processing device has not yet received theleading edge discharging signal of the paper sheet 2 (or the trailingedge discharging signal of the paper sheet 2), the determination resultin step S1401 is NO, and the process of step S1401 repeats until thelocal sheet post-processing device receives the leading edge dischargingsignal (or the trailing edge discharging signal).

The CPU starts the task of the trailing edge of the paper sheet 2 instep S1402 (the task of the leading edge of the paper sheet 3 in FIG.23B). The CPU then specifies the variable “B” (the variable “B′” in FIG.23B) representing the storage area B (the storing area B′ in FIG. 23B)so as to assign the top address “b” (the top address “b′” in FIG. 23B)thereto in step S1403, and the process proceeds to step S1404.

In step S1404, the CPU determines whether the leading edge of the papersheet 2 (the trailing edge of the paper sheet 2 in FIG. 23B) has come atthe discharging position.

When the leading edge of the paper sheet 2 (or the trailing edge of thepaper sheet 2) is present at the discharging position, the determinationresult in step S1404 is YES, and the process proceeds to step S1410.

When the leading edge of the paper sheet 2 (or the trailing edge of thepaper sheet 2) is not present at the discharging position, thedetermination result in step S1404 is NO, and the process proceeds tostep S1405.

In step S1405, the CPU determines whether the local sheetpost-processing device has received the trailing edge discharging signalof the paper sheet 2 (or the leading edge discharging signal of thepaper sheet 3 in FIG. 23B) from the upstream device.

When the local sheet post-processing device has received the trailingedge discharging signal of the paper sheet 2 (or the leading edgedischarging signal of the paper sheet 3), the determination result instep S1405 is YES, and the process proceeds to step S1409.

When the local sheet post-processing device has not yet received thetrailing edge discharging signal of the paper sheet 2 (or the leadingedge discharging signal of the paper sheet 3), the determination resultin step S1405 is NO, and determines whether the local sheetpost-processing device has received a flexible amount of the informationsignals from the upstream device. The “information signals” in stepS1406 represents the various information signals that are receivedbetween the transmission of the leading edge discharging signal of thepaper sheet 2 and the transmission of the trailing edge dischargingsignal of the paper sheet 2. In step S1406 of FIG. 23B, the “informationsignals” represents the various information signals that are receivedbetween the transmission of the trailing edge discharging signal of thepaper sheet 2 and the transmission of the leading edge dischargingsignal of the paper sheet 3.

When the local sheet post-processing device has received a flexibleamount of the information signals, the determination result of stepS1406 is YES, and the process proceeds to step S1407.

When the local sheet post-processing device has not yet received theinformation signals, the determination result of step S1406 is NO, andthe process goes back to step S1404. The CPU repeats steps S1404 throughS1406 until the local sheet post-processing device receives the trailingedge discharging signal or a flexible amount of the information signals.

After the determination result in step S1206 becomes “YES”, the CPUtemporarily writes the received information signals by the number ofaddresses “N” corresponding to the flexible amount of the informationsignals in Group 2-1 (Group 2-2 in FIG. 23B), starting from the topaddress “b” (or the top address “b′” in FIG. 23B) in the storing area B(or the storing area B′) in step S1407. The CPU then increments thevariable “B” (the variable “B′” in FIG. 23B) by the number of addresses“N” according to the flexible amount of the information signals in stepS1408, and the process goes back to step S1404. The CPU repeats stepsS1404 through S1408 until no more sequential information signals forGroup 2-1 (or Group 2-2) is transmitted.

After the determination result in step S1405 becomes “YES”, the CPUdetermines whether the leading edge of the paper sheet 2 (or thetrailing edge of the paper sheet 2 in FIG. 23B) has come at thedischarging position in step S1409.

When the leading edge (or the trailing edge) of the paper sheet 2 hascome at the discharging position, the determination result in step S1409is YES, and the process proceeds to step S1410.

When the leading edge (or the trailing edge) of the paper sheet 2 hasnot yet come at the discharging position, the determination result instep S1409 is NO, and the process of step S1409 repeats until theleading edge (or the trailing edge) of the paper sheet 2 comes at thedischarging position.

After the arrival of the leading edge (or the trailing edge) of thepaper sheet 2 at the discharging position is confirmed in step S1409,the CPU transmits the leading edge discharging signal (or the trailingedge discharging signal in FIG. 23B) to the downstream device in stepS1410, and determines whether the received information signals stillremain in the storing unit of the local sheet post-processing device instep S1411.

When the received information signals still remain in the storing unit,the determination result in step S1411 is YES, and the process proceedsto step S1412.

When the received information signals have completely transmitted and noinformation signals remain in there, the determination result in stepS1411 is NO, and the CPU terminates the process.

After the determination result in step S1411 becomes “YES”, the CPUassigns the top address “b” to the variable “B” (or the top address “b′”to the variable “B′” in FIG. 23B) in step S1412, reads out and transmitsthe received information signals in Group 2-1 (or Group 2-2), startingfrom the top address “b” (or the top address “b′”) to the downstreamdevice in step S1413. The CPU then increments the variable “B” (or thevariable “B′”) by one in step S1414, and the process proceeds to stepS1415.

In step S1415, the CPU determines whether the local sheetpost-processing device has completed the transmission of the informationsignals of Group 2-1 (or Group 2-2) with respect to the downstreamdevice.

When the local sheet post-processing device has completed thetransmission of the information signals of Group 1 (or Group 2-2), thedetermination result in step S1415 is YES, and the CPU terminates thesheet post-processing operation in the local sheet post-processingdevice.

When the local sheet post-processing device still has the informationsignals to be transmitted to the downstream device, the determinationresult in step S1415 is NO, and the process goes back to step S1413 soas to repeat steps S1413 through S1415 until no more sequentialinformation signal to be transmitted for the corresponding paper sheetremains in the storing area B (or the storing area B′) of the storingunit of the local sheet post-processing device.

The transmission timings of the commands or signals used for theabove-described flowcharts of FIGS. 21, 22, 23A are shown in a schematicdiagram of FIG. 24.

As shown in the diagram of FIG. 24, the leading edge discharging signalsthat are indicated as “S1” and “S3” and the trailing edge dischargingsignal that is indicated as “S2” remain in a standby mode while thesesignals S1, S2, and S3 are transmitted from a device 1 representing anupstream device to a device 2 representing a local sheet post-processingdevice, and from the device 2 to a device 3 representing a downstreamdevice. During the respective intervals of the signals S1, S2, and S3 inthe standby mode, the respective groups of the information signals aretransmitted from the upstream device to the downstream device. Aspreviously described, each group of the information signals istransmitted immediately after the corresponding one of the signals S1,S2, and S3. Therefore, the leading edge discharging signal S1 and theinformation signals corresponding to the leading edge discharging signalS1 are transmitted as a set of signals as shown in FIG. 24, and so arethe trailing edge discharging signal S2 and the correspondinginformation signals, and the leading edge discharging signal S3 and thecorresponding information signals.

As previously described in the flowchart of FIG. 14 according to thesecond example embodiment, each of the sheet post-processing devices 6a, 6 b, 6 c, 6 d, and 6 e needs to recognize the timing of conveyance ofa paper sheet.

If the recognition of the timing fails, it may be difficult to assuredlydetermine which request or signal corresponds to which paper sheet orwhich paper sheet and thereafter. Further, if the timing of conveyanceof a paper sheet cannot properly be recognized, the downstream devicecannot perform the paper sheet receiving operation at an appropriatetiming, as previously described.

Further, when the length of the paper sheet is not informed, thedownstream device needs to recognize the timing of receiving thetrailing edge of the paper sheet so as to detect a defect, for example apaper jam. When the timing cannot specifically be recognized, thedownstream device may fail to determine the detection of the paper jamand so forth.

Therefore, the communication procedure performed in the sixth exampleembodiment stores the portion or whole set of the information signals asa group.

Accordingly, as previously described, when the leading edge of the papersheet 1 comes at the discharging position, an upstream device transmitsthe leading edge discharging signal to a downstream device. Immediatelyafter the transmission of the leading edge discharging signal, theupstream device transmits the portion of whole set of the informationsignals corresponding to Group 1-1. When the trailing edge of the papersheet 1 comes at the discharging position, the upstream device transmitsthe trailing edge discharging signal to the downstream device, andimmediately transmits the portion or whole set of the informationsignals corresponding to Group 1-2. Similarly, the operation repeats forGroup 2-1, Group 2-2 and so on. At this time, the received signalsincluding the leading edge discharging signals, the trailing edgedischarging signals, and the information signals are transmitted withoutchanging the sequence order thereof. By keeping the orderly sequence ofthe signals, the downstream device can properly recognize the leadingand trailing edges of a series of paper sheets. For example, the signalsare transmitted in the order of the leading edge of the paper sheet 1,the trailing edge of the paper sheet 1, the leading edge of the papersheet 2, the trailing edge of the paper sheet 2, and so on, which cancause the downstream device to perform the operations smoothly. With theabove-described operation, the present invention can enhance the effectsthat can be obtained through the performance in the fifth exampleembodiment.

Referring to a flowchart of FIG. 25, a communication procedure of anoperation of transmitting signals is described. The local sheetpost-processing device performs the operations of the communicationprocedure to process the information signals in the third through sixthexample embodiments.

In a case in which the local sheet post-processing device receives theinformation signals from the upstream device after the local sheetpost-processing device has already transmitted the preceding paper sheetforwarding signal corresponding to the information signals, to thedownstream device, the local sheet post-processing device instantlytransmits the information signals corresponding to the preceding papersheet forwarding signal, to the downstream device. The “preceding papersheet forwarding signal” can be applied to the leading edge dischargingsignal or the trailing edge discharging signal.

Specifically, the CPU of the local sheet post-processing devicedetermines whether the whole paper sheet forwarding signal(s)transmitted to the local sheet post-processing device have already beentransmitted to the downstream device or have not been received from theupstream device in step S1501.

When the paper sheet forwarding signal(s) in the local sheetpost-processing device have already been transmitted or have not beenreceived, the determination result in step S1501 is YES, and the processproceeds to step S1502.

When the paper sheet forwarding signal(s) remain in the local sheetpost-processing device, the determination result in step S1501 is NO,and the process of step S1501 repeats until the local sheetpost-processing device empties the paper sheet forwarding signalstherefrom.

In step S1502, the CPU determines the local sheet post-processing devicehas received the information signals.

When the local sheet post-processing device has received the informationsignals, the determination result in step S1502 is YES, and the processproceeds to step S1503.

When the local sheet post-processing device has not yet received theinformation signals, the determination result in step S1502 is NO, andthe process of step S1502 goes back to step S1501.

After the determination result of step S1502 has become “YES”, the localsheet post-processing device instantly transmits the received signals tothe downstream device in step S1503, and terminates the process.

By performing the above-described communication procedure shown in theflowchart of FIG. 25, the signals can be aligned in the orderly sequenceand the information signals can be transmitted in the fastest way.

With the operations and tasks as described above according to the firstthrough sixth example embodiments, it is possible to establish a sheetpost-processing system that includes a plurality of sheetpost-processing device, each of which receives various signals includingpaper sheet information by at least one communication module or unitbefore or after the paper sheet is fed, stores the received signals inthe storing unit, and transmits the stored signals before or after thepaper sheet is discharged. Further, each of the plurality of sheetpost-processing devices of the sheet post-processing system keeps theconveying rollers unrotated until the paper sheet forwarding signal isreceived. Further, the sheet post-processing system can be connectedwith an image forming device. With the above-described structures, thesheet post-processing system can perform the sheet feeding operation ina high speed and stable manner and at low cost.

Further, with the operations as described above according to the presentexample embodiment, it is also possible to establish an image formingsystem that includes the sheet post-processing system and the imageforming device connected together with the sheet post-processing system.With the above-described structure, the image forming system can performthe sheet feeding operation in a high speed and stable manner and at lowcost.

The above-described example embodiments are illustrative, and numerousadditional modifications and variations are possible in light of theabove teachings. For example, elements and/or features of differentexample embodiments herein may be combined with each other and/orsubstituted for each other within the scope of this disclosure andappended claims. It is therefore to be understood that within the scopeof the appended claims, the disclosure of this patent specification maybe practiced otherwise than as specifically described herein.

1. A sheet post-processing device comprising: a conveying memberconfigured to convey a sheet-like recording medium; a processing unitconfigured to perform a given operation upon the recording mediumconveyed by the conveying member; a communication unit configured tocommunicate with a device external to the sheet post-processing deviceregarding the given operation performed by the processing unit; and acontrol unit configured to control, via the communication unit,information passing between the sheet post-processing device and theexternal device at a desired timing.
 2. The sheet post-processing deviceaccording to claim 1, further comprising: a storing unit configured tostore information of the recording medium transmitted from the externaldevice, wherein the control unit transmits the information at one of atiming before a discharge of a leading edge of the recording medium anda timing after a discharge of a leading edge of the recording medium. 3.The sheet post-processing device according to claim 2, wherein: thesheet post-processing device receives a forwarding signal to inform atiming of conveyance of the recording medium, and the control unitinitiates a rotation of the conveying member when the sheetpost-processing device receives the forwarding signal and theinformation transmitted from the external device.
 4. The sheetpost-processing device according to claim 2, wherein: the storing unitincludes a first storing unit configured to store at least one signal ofwhole signals corresponding to the information of the recording medium,and when the sheet post-processing device receives the at least onesignal of whole signals during a sheet feeding operation, the controlunit causes the storing unit to store the at least one signal of wholesignals therein and transmits the at least one signal of whole signalsto a different external device disposed downstream thereof, when therecording medium comes at a specified position.
 5. The sheetpost-processing device according to claim 4, wherein: the control unitcauses the storing unit to write a plurality of signals therein in anorderly sequence when the sheet post-processing device receives theplurality of signals and transmits at least one of the plurality ofsignals while keeping the orderly sequence when the recording mediumcomes at the specified position during the sheet feeding operation. 6.The sheet post-processing device according to claim 4, wherein: thesheet post-processing device receives a forwarding signal to inform atiming of conveyance of the recording medium, and the control unittransmits a plurality of signals sequentially at one of a timingimmediately before a transmission of the forwarding signal and a timingimmediately after a transmission of the forwarding signal when therecording medium comes at the specified position during the sheetfeeding operation, the control unit keeping an orderly sequence of theforwarding signal and the plurality of signals according to receiptsthereof.
 7. The sheet post-processing device according to claim 6,wherein: the control unit transmits the forwarding signal including afirst discharging signal, at one of a timing before a discharge of aleading edge of the recording medium and a timing after a discharge of aleading edge of the recording medium, to inform a timing of conveyanceof the leading edge of the recording medium to a different externaldevice.
 8. The sheet post-processing device according to claim 6,wherein: the storing unit includes a second storing unit configured tostore at least one of the plurality of signals received between thefirst discharging signal and a second discharging signal following thefirst discharging signal, the second storing unit storing the at leastone of the plurality of signals as one group unit, and the control unitincludes a transmission unit configured to transmit the firstdischarging signal at one of a timing before a discharge of a leadingedge of the recording medium and a timing after a discharge of a leadingedge of the recording medium, and transmit the at least one of theplurality of signals as one group unit immediately after a transmissionof the first discharging signal.
 9. The sheet post-processing deviceaccording to claim 8, wherein: the transmission unit transmits the firstdischarging signal and the plurality of signals while keeping an orderlysequence thereof.
 10. The sheet post-processing device according toclaim 6, wherein: the control unit transmits the forwarding signalincluding a first discharging signal, at one of a timing before adischarge of a leading edge of the recording medium and a timing after adischarge of a leading edge of the recording medium, to inform a timingof conveyance of the leading edge of the recording medium to a differentexternal device, and the control unit transmits the forwarding signalincluding a second discharging signal, at one of a timing before adischarge of a trailing edge of the recording medium and a timing aftera discharge of a trailing edge of the recording medium, to inform atiming of conveyance of the trailing edge of the recording medium to adifferent external device.
 11. The sheet post-processing deviceaccording to claim 6, wherein: the storing unit includes a secondstoring unit configured to store at least one of the plurality of firstsignals received between the first discharging signal of a firstrecording medium and the second discharging signal of the firstrecording medium following the first discharging signal thereof as afirst group unit, and also store at least one of the plurality of secondsignals received between the second discharging signal of the firstrecording medium and a third discharging signal of a second recordingmedium following the second discharging signal of the first recordingmedium as a second group unit.
 12. The image reading device according toclaim 11, wherein: the control unit includes a transmission unitconfigured to transmit the first discharging signal of the firstrecording medium at one of a timing before a discharge of a leading edgeof the first recording medium and a timing after a discharge of aleading edge of the first recording medium, transmit the at least one ofthe plurality of first signals as the first group unit immediately aftera transmission of the first discharging signal of the first recordingmedium, transmit the second discharging signal of the first recordingmedium at one of a timing before a discharge of a trailing edge of thefirst recording medium and a timing after a discharge of a trailing edgeof the first recording medium, and transmit the at least one of theplurality of second signals as the second group unit immediately after atransmission of the second discharging signal of the first recordingmedium.
 13. The image reading device according to claim 12, wherein: thetransmission unit transmits the first discharging signal, the seconddischarging signal and the plurality of signals while keeping an orderlysequence thereof.
 14. The sheet post-processing device according toclaim 6, wherein: when the plurality of signals are received after atransmission of the forwarding signal corresponding to the plurality ofsignals to a downstream external device disposed downstream of the sheetpost-processing device, the control unit transmits the plurality ofsignals instantly to the downstream external device.
 15. A sheetpost-processing system comprising: a connecting member; and a pluralityof sheet post-processing devices at least some of which are connected bythe connecting member, each sheet post-processing device including atleast the following, a conveying member configured to convey asheet-like recording medium; a processing unit configured to perform agiven operation upon the recording medium conveyed by the conveyingmember; a communication unit configured to communicate with a deviceexternal to the sheet post-processing device regarding the givenoperation performed by the processing unit, a control unit configured tocontrol, via the communication unit, information passing between thesheet post-processing device and the external device at a desiredtiming, a storing unit configured to store information of the recordingmedium transmitted from the external device; wherein the plurality ofsheet post-processing devices other than a most downstream sheetpost-processing device store at least one signal to the storing unit ata receipt of the at least one signal during a sheet feeding operationand transmits the at least one signal when the recording medium comes ata specified position.
 16. An image forming system, comprising: an imageforming device configured to form an image on a surface of a recordingmedium; and a plurality of sheet post-processing devices at least someof which are connected by the connecting member, each sheetpost-processing device including at least the following a conveyingmember configured to convey a sheet-like recording medium, a processingunit configured to perform a given operation upon the recording mediumconveyed by the conveying member, a communication unit configured tocommunicate with a device external to the sheet post-processing deviceregarding the given operation performed by the processing unit, and acontrol unit configured to control, via the communication unit,information passing between the sheet post-processing device and theexternal device at a desired timing; wherein a most upstream sheetpost-processing device of the plurality of sheet post-processing devicesis connected to the image forming device.
 17. The sheet post-processingsystem of claim 15, wherein the control unit transmits the informationat one of a timing before a discharge of a leading edge of the recordingmedium and a timing after a discharge of a leading edge of the recordingmedium.
 18. The sheet post-processing system of claim 17, wherein: thesheet post-processing device receives a forwarding signal to inform atiming of conveyance of the recording medium, and the control unitinitiates a rotation of the conveying member when the sheetpost-processing device receives the forwarding signal and theinformation transmitted from the external device.
 19. The image formingsystem of claim 16, wherein the control unit transmits the informationat one of a timing before a discharge of a leading edge of the recordingmedium and a timing after a discharge of a leading edge of the recordingmedium.
 20. The image forming system of claim 19, wherein: the sheetpost-processing device receives a forwarding signal to inform a timingof conveyance of the recording medium, and the control unit initiates arotation of the conveying member when the sheet post-processing devicereceives the forwarding signal and the information transmitted from theexternal device.